Redundant computer system utilizing comparison diagnostics and voting techniques

ABSTRACT

A redundant computer system utilizing comparison diagnostics and voting techniques includes a plurality of redundant channels. Each pair of the processors receives/obtains process information from I/O modules via dual redundant sensors (DRS). The processors execute an application program, whereby output module is utilized for comparing output data of the two processors. Output module receives output data from neighboring modules, if there is a deviation or other disparity in the output data. Each pair of processors, a voter and an improper sequence detector component disables the output module, if a majority of signals vote that output module fails. In addition, the system uses 2-of-3 voting, the system remains operational in the presence of up two transient or hard failures.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims the benefit of U.S. provisional patentapplication No. 62/531,557 filed on Jul. 12, 2017, and U.S. provisionalpatent application No. 62/513,468 filed on Jun. 1, 2017, the contents ofwhich are incorporated herein by reference.

TECHNICAL FIELD

The embodiments disclosed herein generally relate to redundant computersystems. Particularly, the embodiments disclosed herein relate toredundant computer systems that utilize a combination of comparisondiagnostics and voting techniques. More particularly, the embodimentsdisclosed herein relate to redundant computer systems that utilize acombination of comparison diagnostics and majority voting techniques toachieve enhanced fault tolerance.

BACKGROUND

Computer systems for use in critical applications, such as those used insafety systems, and process control systems, are susceptible to systemfailures. In some circumstances, failures of these critical systems mayexpose entities to a potentially fatal event, as well as to significanteconomic loss. For example, such safety-critical control systems areutilized to provide control in critical applications, such ashigh-integrity pressure protection pipe line systems, emergency stopsystems, such as those utilized on drilling platforms, nuclear controlsystems, oil refinery safety and control systems, boiler controlsystems, turbo-machinery control systems, and off-shore fire and gasprotection systems. To avoid failure, such critical systems monitorvarious operational processes, such that if a selected value that isassociated with a particular process exceeds a predetermined thresholdthat is indicative of a dangerous operational state, the system takesthe necessary action to avoid the occurrence of a complete failure, suchas by halting the process or placing the process in a “safe” state.However, in some circumstances, a critical system may perform a “safe”failure of a process, whereby the system mistakenly performs a shutdownprocess when a shutdown is, in fact, not required. Furthermore,unplanned shut downs resulting from such “safe” failures require asubsequent re-start of the critical process, which leads to lostproduction and time, which is not desirable. However, if the monitoringsystems fail to identify the hazardous or dangerous system parameters orconditions of a critical computing system, a dangerous system failuremay occur, which may result in the loss of human life or substantialdamage to the operating components or machinery controlled by theprocess.

In order to avoid the failure of critical computer systems that areresponsible for controlling these critical processes, various standardsor protocols are utilized to allow such critical computer system toachieve high levels of fault tolerance. Such standards and protocolsthat may be utilized by these critical computer systems. For example,such critical computer systems may utilize safety integrity level 4 (SIL4) fault tolerance, as is provided by IEC-61508 and IEC-61511 standards.In addition, such critical computer systems may utilize the Planar 4system. Planar 4 is based on a hard wired modular electronic circuit,which incorporates fail safe logic that is built into each circuit. ThePlanar 4 system is certified in accordance with IEC 61508 to a SIL of ¾.Current fault-tolerant systems, such as that provided by Planar 4,utilize a hard-wired computing architecture, which cannot be easilychanged or adapted for use in different applications or processes wherefault-tolerant control is desired. For example, U.S. Pat. No. 7,877,627describes a computing system that withstands multiple failures, whilestill maintaining safety. This system includes three primary processormodules that operate in parallel on a cyclical basis. This computersystem further includes three redundant processor modules that alsooperate cyclically in parallel. A first, second, and third primaryprocessor module are respectively connected to associated first, secondand third primary input modules to receive input data therefrom and touse this data as an input for an application program that is executed byeach primary processor module. A first, second and third redundantprocessor module are respectively connected to associated first, secondand third redundant input modules to receive input data therefrom and touse this data as an input for an application program that is executed byeach redundant processor module. The system further includes an outputmodule that includes first, second and third output module or circuits,which may comprise any suitable output interface electronics thatenables the output of data therefrom. Each output module houses a firstand a second interface for receiving output data from the primary andredundant processor modules respectively. The primary processor module(PPM) is connected to the associated redundant processor module (RPM)and sends a command to the RPM in order to initiate the execution of oneinstance of the application program at the same time that the PPM beginsexecution of another instance of the application program. The PPM andthe RPM, therefore, synchronously execute the application program. Theoutput module receives output data from both the associated PPM and RPMclose in time during each cycle of the system operation. During normalsystem operation, each output module generates output data that isproduced by the associated PPM and RPM that are equal, and the outputmodule uses output data that is received from the PPM. In the event thatthe PPM fails permanently, the associated output module uses the outputdata produced by the RPM. In the event a disparity between the outputdata that is produced by the PPM and the RPM for some controlled pointsin a process is discovered, the result of one of the PPM or associatedRPM is identified as producing erroneous output data, which is theresult of the occurrence of a transient fault in the fault-tolerantcomputer system. Each output module compares output data that isreceived from the PPM and the associated RPM to identify whether apossible disparity exists among output data for each controlled point.In the event that a disparity is discovered, the output module disablesits own output data for controlled points where a disparity has beenidentified. The output module communicates with each other during eachcycle of the computing system operation in order to receive output dataof neighboring output module. During normal system operation, eachoutput module has its own output data, and each output module operatesto calculate a logical sum of the output data that it receives from theneighboring output module. The output module further includes a votingnetwork that receives output data directly from the output module andoutput data that output module received from neighboring output modules.Each voting network includes three electronic switches, such astransistors, that are connected in series. Three of the voting networksare controlled by output data produced by an associated output modulebased on a first output, and by output data that is the aforementionedlogical sum of the electronic valves of different voting networks, thatare connected in parallel. Such a configuration provides a systemoutput, which is the result of 2-of-3 majority voting among the outputdata that the associated output module has received from the associatedprimary processor module (PPM) or from the redundant processor module(RPM).

The fault-tolerant computer system of the '627 patent may be configuredto be operational in the presence of up to two faults. However, the '627system utilizes a simple watchdog timer (WDT) as its only diagnosticsystem. The WDT periodically monitors an associated output module of thecomputer system, and disconnects the output module from participation inthe computer system output when the output module fails. Unfortunately,it is difficult to configure the WDT to detect faults with a probabilitythat is greater than about 90%. Accordingly, the WDT is unable toeffectively discover failures that may occur in the output module of thefault-tolerant computer system. Thus, in some circumstances, if theoutput controller in the output module fails due to a hard failure, andthis failure is not discovered by the WDT, the system performs a “falsetrip”. A false trip may lead to substantial financial losses, as well assignificant harm to property or to the individual. Another disadvantageof such system is that it has about double the number of input modules,which increases the overall cost of the system. Furthermore, thisfault-tolerant computer system unfortunately does not include variantsto allow it to operate with input/output (I/O) modules that are locatedin close proximity to a controlled process, but that are also far awayfrom a central computing unit or processor.

A safety instrumented system (SIS) includes two identical channelshaving a read-back diagnostic, which enables the system to operate inthe presence of any single failure. Such SIS systems, unfortunately, arenot able to tolerate the occurrence of two concurrent faults.Accordingly, the various embodiments of the system discussed hereinprovide a dual-channel SIS that includes a diagnostic that allows thesystem to remain operational after the occurrence of some kinds of twoconcurrent faults.

U.S. Patent No. 2016/0283426 describes a control system comprising afirst and a second controller module, where each controller moduleincludes management circuitry that identifies which controller moduleoperates in a master mode or a slave mode. This control system operateswith the first controller module, but switches to a second controllermodule when the first controller module fails. Unfortunately, suchsystem has no means for determining which controller module is the firstor second by default after power up. In contrast, the variousembodiments of the redundant computer system disclosed herein include aprimary and a secondary processor module, with each processor moduleincluding hardware and software means that define which processor moduleis by default the primary or secondary processor module. In addition,such hardware and software means of the various embodiments of theredundant computer system also continuously enables each processormodule to change from a primary status to a secondary status in theevent that the primary processor module fails.

Therefore, there is a need for a fault-tolerant computer system thatovercomes the deficiencies of the current systems, including that of the'627 patent and the '426 publication, discussed above, and thatprovides, in some embodiments, uninterrupted system operation that iscapable of attaining safety levels in accordance with one or morestandards/protocols, such as SIL 4/IEC 61508 for example.

SUMMARY

The various embodiments of the redundant computer system provide ahighly reliable system, which utilizes the same basic components, but indifferent numbers, to allow a vendor of the redundant computer systemand an end user to configure a system that has an effective combinationof reliability/availability and cost in order to meet desired operatingrequirements. In various embodiments, the system utilizes comparisondiagnostics and voting techniques that allow the system to remainoperational in the presence of multiple permanent and/or transientfaults. At least one embodiment is designed to allow an industrialcontrol system to provide a high level of fault tolerance and safety,such as up to SIL 4 for example, which is required for extremelycritical applications. It should be appreciated that the system can beimplemented in additional embodiments, and may be adopted for use in avariety of applications, including railroad safety, aircraft safety,vehicle safety, as well as many other safety responsible applications.

One embodiment, referred to as an ultra-reliable computer system (URS),includes three identical channels operating in parallel. Each channelincludes two processor modules; each containing one pair of primary(PPM) and secondary (SPM) processor modules, one or more input andoutput modules, each output module includes an output controller, alogic circuit and a voting network. The primary processor modules areconnected to each other through a first communication bus to synchronizetheir operation. Secondary processor modules are also connected to eachother through a second communication bus to enable their synchronizedoperation. In addition, the primary and secondary processor modules ineach channel are connected together through a third communication busfor synchronization between the PPM and the associated SPM. Each inputmodule includes a first and a second interface that are respectivelyconnected to the associated PPM and SPM through a first and a second I/Obus. Each pair of primary (PP) processors is separately coupled to anassociated input module so that it receives information via the dualredundant sensors (DRS) that are used to monitor operating parametersdata of a controlled point of a controlled process. Each DRS integratesa first and a second section in a single hardware package that measuresthe same parameter for each desired point in the controlled process. Thesystem performs safety and control functions on a cyclical basis,whereby the operation cycle period of the system is defined by a scantime, which includes, but is not limited to: the time required for inputdata polling, the time required for application program execution, andthe time required for the transfer of output data to the output modules.In some embodiments, the application program execution and input datapolling may be overlapped. Input and output modules and correspondedredundant sensors can be digital or analog.

During normal operation of the redundant computer system, the outputdata that is produced by the associated PPM and SPM in each channel areequal, and the output controller by default uses output data that isreceived from the PPM. In addition, the output controller (OC) comparesthe output data that is received from the associated PPM and SPM toidentify whether a possible disparity exists between the output data forsome controlled point of the controlled process. The OC in each channelis connected with the output controllers in neighboring channels over aread-only bus for receiving/sending output data to/from the outputcontrollers in the neighboring channels. If both the PPM and SPM arehealthy, but a disparity exists between their output data, thiscondition is interpreted to indicate that either the PPM or SPM isproducing erroneous data. Such deviation in data may, in somecircumstances, be due to a deviation between input data produced by afirst and a second section of the DRS, or due to occurrence of transientfaults. The output data with disparity is counted as “doubtful”, andbecause of that, the output controller activates a disparity signal Dindicating that the system is not utilizing this doubtful data. Next,the output controller receives output data from neighboring outputcontrollers to substitute the doubtful output data and sends these datato the associated logic circuit. As described above, this comparisondiagnostic allows the system to discover the occurrence of anydisparity, and to reconfigure the system to allow it to overcome theeffect of the disparity on the operation of the system in a moreefficient and effective manner than that of current systems.

Each logic circuit performs a certain logic operation with theassociated voting network (VN). For example, the outputs of the VN ineach channel are configured by using three electronic switches, such astransistors or relays for example, that are connected in series betweenan associated power supply and a load of the system for each controlledpoint. The three electronic switches are connected in parallel, withtheir outputs in different channels, and connected together to providethe system output to be a result of two-out-of-three (2-of-3) votingamong the output data that is produced by three channels during normalsystem operation. Such configuration of the VN continues to beoperational in the presence up to two points of failure. The system,thereby, continues to perform 2-of-3 voting in the event that up tothree PPMs or up to three SPMs fail concurrently. The system, therefore,provides a very high level of fault tolerance with respect to hardfaults, which may occur in the PPM or in the SPM. The system continuesoperate in the presence of disparity in one or two channels, the systemmay perform a safe shutdown for the process, if the disparity occurs inall channels concurrently. If only a single output controller has thedisparity, the system performs 2-of-2 voting among the output data thatis produced by two neighboring channels. The system performs 1-of-1voting if the disparity occurs in two channels for the same controlledpoints in the process.

The redundant computer system further includes a triple redundantdiagnostic system in each channel, whereby the diagnostic systemincludes a 2-of-3 voter component that is coupled with the output of animproper sequence detector (ISD) and is coupled with the separatecommunication lines of the PPM and SPM. The improper sequence detector(ISD) monitors the associated output controller to verify thetime-based, logical program that the output controller performs. The PPMand SPM in each channel uses the associated I/O bus to verify thecondition of the associated output controller and uses separatecommunication lines to control output of the 2-of-3 voter component(VC).

The VC includes at least three parallel voting groups, with each groupincluding at least two small power electronic switches, such astransistors, connected in series. This configuration of the 2-of-3 VC isable continues to be operational in the presence a fault in any oneswitch and may to be operational in the presence of some kind of twofaults in two switches. The VC receives three input signals from thePPM, SPM, and the ISD. The VC produces an output signal on inputs of thelogic circuits in each channel, as the result of majority voting amongsignals of the associated PPM, SPM, and ISD. If at least two componentsamong the PPM, the SPM, and the ISD vote that the output controllerfails, the logic circuit drives the electronic switches of theassociated channel to an OFF state, so as to de-energize output of theassociated channel. This triple redundant diagnostic process allows thesystem to operate with one working output controller in the event thattwo output controllers concurrently fail in two channels. Furthermore,this triple redundant diagnostic system, which has no single point offailure, is considerably more effective than diagnostic systems that arecurrently used.

Continuing, the impact of the occurrence of faults in the logic circuit(LC) and in the output voting network (VN) are considered. The VN ineach of the three channels performs 2-of-3 voting by using three seriesconnected electronic switches, such as transistors or relays, which areprovided in each channel. Each of the electronic switches is normally inan ON state, so as to energize a load of the system. The VN uses oneelectronic switch in each channel as a fault recovery valve (FRV). Assuch, if any two electronic switches in different channels are stuck orfixed in an OFF state due to a permanent failure, the system will remainoperable with the one channel that continues to energize the load. Iftwo electronic switches in the same channel are stuck or fixed in the ONstate due to a permanent failure, such condition can lead to a dangeroussystem failure, since the load cannot be de-energized when thecontrolled process requires it. Furthermore, each output controllerchecks the condition of the three electronic switches by usingconventional ongoing diagnostics, and sets a signal on the input of theFRV, which drives this switch to an OFF state, so as to de-energize theoutput of the associated channel. This allows the system to avoid adangerous failure in the event that two electronic switches in seriesare stuck in an ON state. The system, therefore, continues to remainoperational in the presence of up two faults of the electronic switchesin two channels. Each logic circuit has no single point for a dangerousfailure, but due to a single fault, it can set the associated electronicswitch to an OFF state. In the event that two neighboring logic circuitsconcurrently fail in two associated channels, the system continues toremain operational using a third channel in the presence of two suchfaults. In some embodiments, the system in generally able to tolerate upto two fault occurrences in any combination of the logic circuit and theoutput controller. The system also performs a shutdown process toprovide a safety condition to the controlled process if all systemchannels concurrently fail. As previously discussed, the system is ableto remain operational in the presence of up to two hard or transientfaults, and may operate properly on the occurrence of some types ofthree faults.

In another embodiment, a dual duplicated computing system (DDS) isprovided, which is similar to the ultra-reliable computer system (URS)previously discussed. Accordingly, the DDS system includes twoduplicated channels A and B, with each channel including a primary and asecondary processor module (PPM and SPM) that operate together inparallel. As such, the DDS system has the same primary functionalcomponents as the URS system, but the total number of components of theDDS system is 1.5 times less than in the URS system. Thus, the DDSsystem is substantially less expensive as compared to the URS system. Aswell as the URS, the DDS utilizes an effective fault diagnostic processthat has no single point of failure. During normal operation, the DDSperforms 2-of-2 voting between the output data that is produced by thePPM and the SPM in two channels. The output controller uses an embeddedwatchdog timer to verify whether the associated PPM and SPM havedelivered output data on time or not. If the output data has not beendelivered on time, the watchdog sends signal to the logic circuit that,in-turn, disables the outputs of this channel in the event that both thePPM and the SPM in the same channel concurrently fail. When a disparityoccurs, the output controller (OC) excludes doubtful output data from asystem output, and this output data is substituted by the output datathat the OC received from neighboring output controller. The outputs ofthe logic circuit are connected with the inputs of the voting network(VN). The output controller sends signals to the logic circuit that,in-turn, disables the outputs of this channel, but the DDS continues tooperate with a single healthy channel. In addition, conventionaltechnology, such as SEC-DED, may be used in each channel for thedetection/correction of faults, such as transient faults. The systemcontinues to perform 2-of-2 voting in the event that up to two PPMs orup to two SPMs located in different channels fail concurrently due tothe occurrence of hard (permanent) faults. This system also provides adecreased cost factor, as compared to the URS system, withoutsacrificing operational reliability. The DDS is also capable ofachieving certification of up to SIL 3 in accordance with standards61508 and 61511.

In another embodiment, a dual channel computing system (DCS) isprovided, which includes two channels A and B that are similar instructure and operation to the dual channels of the DDS system. That is,the DCS system has the same primary functional components that the DDSutilizes, but the total number of DCS components is about 2 times lessthan that used in the DDS. In comparison to the ultra-reliable computersystem (URS), the DCS has about 3 times less components, and due tothis, the DCS is less costly than the URS system. During normal systemoperation, the DCS performs two-out-of-two (2-of-2) voting between theoutput data that is produced by the central processors CP A and CP B inchannels A and B respectively. The output controller (OC) in eachchannel is connected with the output controller in neighboring channelover a read-only bus for receiving/sending output data to/from theoutput controller in the neighboring channel. The output controller usesan embedded watchdog timer to verify if the associated CP A and CP Bhave delivered output data on time or not. If the output data has notbeen delivered on time, the watchdog sends signal to the logic circuitthat, in-turn, disables the outputs of this channel in the event thatboth the PPM and the SPM in the same channel concurrently fail.

In addition, the DCS introduces a new configuration that allows the CP Aand the CP B to send output data to both the output controllers A and Bat the same time to increase the reliability and availability of thesystem. For example, if the CP A and the output controller, which arelocated in different channels concurrently fail, the DCS continues toremain operational with the healthy CP B in channel B and with thehealthy output controller in channel A. If the CP B and the outputcontroller, which are located in different channels concurrently fail,the DCS continues to remain operational with the healthy CP A in channelA and with the healthy output controller in channel B. If both the PPMand the SPM in the same channel are healthy, but a disparity existsbetween their output data, such a condition is interpreted to indicatethat the PPM or SPM is producing erroneous data due to occurrence oftransient faults. The output data with disparity is counted as“doubtful”, and because of that, the output controller activates adisparity signal D, which indicates that the system is not utilizingthis doubtful data. The output controller then receives output data fromneighboring output controller to substitute the doubtful output data andsends these data to the associated logic circuit.

The redundant computer system further includes a triple redundantdiagnostic system in each channel, whereby the diagnostic systemincludes a 2-of-3 voter component that is coupled with the output of animproper sequence detector (ISD) and is coupled with the separatecommunication lines of the PPM and SPM. The improper sequence detector(ISD) monitors the associated output controller to verify thetime-based, logical program that the output controller performs. The PPMand SPM in each channel uses the associated I/O bus to verify thecondition of the associated output controller and uses separatecommunication lines to control output of the 2-of-3 voter component(VC).

The VC includes at least three parallel voting groups, with each groupincluding at least two small power electronic switches, such astransistors, connected in series. This configuration of the 2-of-3 VC isable continues to be operational in the presence a fault in any oneswitch and may to be operational in the presence of some kind of twofaults in two switches. The VC receives three input signals from the CPA, CP B, and the ISD. The VC produces an output signal on inputs of thelogic circuits in each channel, as the result of majority voting amongsignals of the associated CP A, CP B, and ISD. If at least twocomponents among the CP A, the CP B, and the ISD vote that the outputcontroller fails, the logic circuit drives the electronic switches ofthe associated channel to an OFF state, so as to de-energize output ofthe associated channel. This triple redundant diagnostic process allowsthe system to operate with one working output controller in the eventthat two output controllers concurrently fail in two channels.Furthermore, this triple redundant diagnostic system, which has nosingle point of failure, is considerably more effective than diagnosticsystems that are currently used. This feature allows the DCS to toleratetwo faults, which significantly increases the reliability andoperational availability of the system. In general, the DCS providesfault tolerance to any single point of failure stemming or resultingfrom either a permanent or a transient fault and continues to operate inthe presence of some type of two faults. The DCS is also capable ofachieving certification of up to SIL 3 in accordance with standards61508 and 61511.

Another embodiment of the redundant computing system that includes acomputer system 14 that integrates a safety section 14 a and controlsection 14 b that provides separate safety and control functionality.The safety section 14 a and the control section 14 b operateindependently and have physical separation protection layers.Considering first the safety section 14 a, it is includes a main chassishousing two redundant central processors, CP A and CP B, that operate inparallel, and include multiple remote chassis to provide safety controlfor up to four or more processes at the same time. CP A and the CP Bhave an embedded communication module for enabling communication betweenthe CP A and CP B, and are connected to an isolated bus to providecommunication between the safety and control sections of the integratedsystem. In the event that the physical parameters measured by the safetysection deviate away from the safety range, the safety section informsthe PC A and the SC B that the controlled process may be in a dangerouscondition. If the safety and control sections cannot overcome thedangerous condition, the safety section brings the controlled processinto a safety state.

In addition, the CP A and the CP B use this bus for communication withexternal devices, such as a host device and an operator interface. Eachcentral processor further includes at least one embedded ETHERNET port,or other network communication interface, that consistently communicateswith multiple remote chassis via external ETHERNET switches. Each remotechassis (FIGS. 9A-B) includes at least two input/output controllers(IOC) that are connected over a corresponding I/O (input/output) bus toI/O (input/output) modules for receiving/sending input/output data.Input module in each channel receives process information from a singlesensor for each controlled point and sends this information to theassociated central processor via IOC, which, in turn, transfers it overa long distance data bus. Each CP A and CP B uses an embedded ETHERNETport and an ETHERNET switch for scanning the IOC over a long distancedata bus, which may be a fiber optic or copper cable, as well as anyother communication medium for example. The safety section performssafety functions on a cyclical basis, whereby the operation cycle periodis defined by the scan time. During each scan, the CP A and the CP Breceive input data from the associated IOC that obtained it from thecorresponding input module, then the CP A and the CP B synchronouslyexecute an application program, whereupon and they send output data tothe associated IOC.

In general, the safety section operations are similar to the operationof the dual channel system (DCS) previously discussed, but the safetysection additionally uses two IOCs for managing the I/O function in theremote chassis, which is absent in other embodiments. Each remotechassis further includes at least two input modules, each of whichreceives input data that is produced by a single sensor for eachcontrolled point. In the event that the input data exceeds the secondlimit, the CP A and the CP B section sends an alarm signal to thecontrol section, thereby notifying the occurrence a dangerous failure.Furthermore, conventional technologies, such as SEC-DED, may be used ineach channel for the detection/correction of faults, such as transientfaults. It should be appreciated that the safety section may operate inthe presence of any single hard (permanent) failure and may operate inthe presence of some kinds of two transient faults. After the occurrenceof two hard failures, the system output is de-energized, whereupon asafety shutdown of the process is performed.

In still another embodiment, the control section 14 b of the ISC systemincludes two identical process controllers, such as a primary controller(PC A) and a secondary controller (SC B), which are arranged in aback-up redundant configuration that is located on a main chassis. ThePC A and the SC B operate in a commonly used mode, whereby the PC Aoperates in an active mode providing all communications withinput/output devices and with other devices, while the SC B is placed ina hot standby mode. The control section further includes a multipleremote chassis, each of which housing at least two input/outputcontrollers (IOC). Each IOC operatively communicates over I/O bus withthe associated input modules 1−N for receiving input data from controlinputs. These control inputs can be, for example, from flow and pressuresensors, although other inputs can be used. Specifically, each IOC makestwo copies of the input data and send them respectively to the PC andSC. Only the PC A is selected, however, for sending the results of theapplication program execution to the associated IOC. Each processcontroller further includes at least one embedded ETHERNET port thatconsistently scanning the associated IOC in multiple remote chassis viaexternal ETHERNET switches through long distance buses that can be fiberoptic or copper cables, as well as any other communication medium forexample. Such that in each scan, the PC A and the SC B receive inputdata from the associated IOC that obtained it from corresponding inputmodule; PC A and the PC B then synchronously execute an applicationprogram. The control section performs control functionality on acyclical basis, whereby the operation cycle period is defined by thescan time. A result of the application program execution is sending asoutput data back to associated IOC only by primary controller. In theevent that primary controller fails, the secondary controllerautomatically obtains primary status. In the event that secondaryprocess controller fails, the primary process controller holds theprimary status. Faulty process controller should be replacing online bya new one that immediately obtains the secondary status.

The firmware and hardware of the control section of the redundantcomputer system may include a self and mutual diagnostic system that PCA and SC B perform periodically with each scan of the operating cycle.This diagnostic allows the status of PC A and SC B to be determined,while allowing their statuses to be changed from PC to SC and from SC toPC in the event that the PC or the SC fails (FIGS. 10, 11AA-AC,11BA-BC). In the event that the PC fails, the secondary controlleroperates in a stand-alone mode changing secondary status to primary. Inthe event that the SC fails, the primary controller operates in astand-alone mode, while retaining primary status. In addition, the PC Aand SC B use this diagnostic process for synchronized operation of thePC A and SC B. Furthermore, the diagnostic process is able to define, bydefault, what status PC A and SC B have, based on their location on themain chassis. The diagnostic process contains a method to manage allcontrol section operations that include the change in PC and SC statusin the event that the PC or the SC fails. The control section and thesafety section operate independently, and have physical separationprotection layers. The safety section, thereby, further increases thesafety level of the control system section. Because of suchconfiguration, the integrated systems is capable of meeting up to SIL 3requirements in accordance with standards IEC 61511-1 11.2.4.

A redundant computer system comprising a first channel, a secondchannel, and a third channel each channel comprising primary processor;a secondary processor, wherein said primary processor is in operativecommunication with said secondary processor, said primary and secondaryprocessor operate in parallel redundancy; said primary processor in thefirst channel, said primary processor in the second channel, and saidprimary processor in the third channel are in operative communicationwith each other; said secondary processor in the first channel, saidsecondary processor in the second channel, and said secondary processorin the third channel are in operative communication with each other; aninput module includes in each channel a first and a second interface toprovide operative communication of said input module with said primaryand secondary processor, wherein said input module in each channel is inoperative communication with a first and a second section of a dualredundant sensor (DRS) for each controlled point that delivers inputdata to said input module; said input module including means forcalculating a deviation between values of said input data produced bysaid first and second section of the DRS for each controlled point toindicate whether said deviation is within a predetermined limit; saidinput module can be digital or analog; said primary processor and saidsecondary processor in each channel configured to receive said inputdata from said input module to synchronously execute an applicationprogram and to transfer output data as a result of said applicationprogram execution to an output module via a first and a secondinterface; said output module in each channel includes an outputcontroller that is in operative communication with said PPM and withsaid SPM for receiving said output data from the PPM and from the SPM;said output module further includes a voter component and an impropersequence detector (ISD) component; said output module can be digital oranalog; said voter component is in operative communication with said PPMand said SPM, said ISD component is in operative communication with saidvoter component and with said output controller; means in said impropersequence detector that verifies an absence or presence a fault intimetable and verifies consistency of program operations in said outputcontroller; a comparing diagnostic in said primary processor module(PPM) and said secondary processor module (SPM) in each channel formonitoring a condition of said output module, said comparing diagnosticincludes a voter component and includes an improper sequence detector(ISD) component; said comparison diagnostic allows the system to disablesaid output module if at least two elements among the PPM, the SPM, andthe ISD vote that said output controller has failed; said comparisondiagnostic having no single point of failure to allow the system tooperate with one operational output module in the event that twoneighboring output modules fail concurrently; said output controllerconnected via a read only bus with a neighboring output controller toreceive or send said output data from or to said neighboring outputcontrollers; means wherein said output controller includes foractivating a disparity signal on an input of said logic circuit for somecontrolled points if the associated PPM and SPM produce said output datathat are different due to occurrence of transient faults, or due to saiddeviation that is out of said predetermined limits for said controlledpoints; said disparity signal being activated as a result of anexclusive NOR (XNOR) operation between single-bit output data that saidoutput controller receives from the associated PPM and SPM; said outputdata is substituted by the output data produced by neighboring outputcontrollers for some controlled points if said disparity signal isactivated for said controlled points; said logic circuit includes ineach channel an arrangement of a plurality of logic gates that arecoupled through isolated drivers with inputs of said voting network foreach controlled point; said logic circuit in said first channelproviding the outputs of the associated voting network as a product ofsaid output data that is received from said output controller in thefirst channel and a sum of said output data received from outputcontrollers in said second and third channels; said logic circuit insaid second channel providing outputs of the associated voting networkas a product of said output data that is received from said outputcontroller in said second channel and a sum of said output data receivedfrom said output controllers in said first and third channels; saidlogic circuit in said third channel providing outputs of the associatedvoting network as a product of said output data that is received fromsaid output controller in said third channel and a sum of said outputdata received from said output controllers in said first and secondchannels; said logic circuit and voting network performing a logicoperation with said output data to provide 2-of-3 voting among outputdata produced by said first, second, and third channel; said votingnetwork including a fault recovery valve for each controlled point toallow said voting network to remain operational in the presence of uptwo faults; the system continuing to perform 2-of-3 voting even thoughthree PPMs or three SPMs concurrently fail, thereby, allowing the systemto continue to remain operational in the presence of multiple faults inthe PPM and in the SPM; the system energizes a controlled process in thefault free operation when a majority of system channels operate properlyand de-energizes said process in the presence of multiple dangerousfailures in the system; the system continues to operate in the presenceof any two faults in one or two channels, the system providing a safeshutdown for the process if hard faults occurs in all channels; each PPMuses same hardware and same software, which are different with hardwareand software that each SPM uses, said hardware and software diversityallows the system decreasing the probability of common cause failure.

The redundant computer system of claim 1, wherein said voter componentincludes a plurality of parallel voting groups that are coupled betweena voltage source and a ground node, with each voting group including atleast two low power switches, such as a MOSFET or any other suitabletransistor or relay for example, connected in series; said primary andsecondary processor in each channel continually controlling saidswitches in two groups by the associated lines, while the switches inthe third group is controlled by said ISD; said voter component producesan output signal as a result of a majority of two-out-of-three votingamong signals, which the primary and a secondary processor and the ISDproduce on the inputs of said voter component; said output signal ineach channel is connected to a corresponding input of said logic circuitthat disconnects output of the associated channel from output of thesystem if said majority of two-out-of-three signals vote that saidoutput controller fails; a logic circuit in each channel includes anarrangement of plurality of a logic gates, the inputs of saidarrangement is in operative communication with said output controller;outputs of said arrangement is in operative communication with inputs ofsaid voting network via an isolation drivers; said logic circuit is inoperative communication with said output controller and in operativecommunication with said voting network, said voting network includesthree switches in series for each controlled point that is in operativecommunication with said logic circuit, said three switches in saidfirst, second, and third channels are coupled in parallel for eachcontrolled point for providing an output of the system; in normaloperation, the system performs 2-of-3 voting among output data producedby said first, second, and third channel; a single output controllerexcludes an own output data from outputs of said logic circuit and usesoutput data received from the neighboring output controllers, the systemthen performs the 2-of-2 voting instead of 2-of-3 voting if saiddisparity signal is activated in said single output controller for somecontrolled points; said output controllers in two channels excludes anown output data from outputs of said associated logic circuits and usesoutput data received from the neighboring output controllers, the systemthen performs the 1-of-2 voting instead of 2-of-3 voting if saiddisparity signal activates in said two channels of the system for somecontrolled points; the system, continues to operate in the presence ofsaid disparity in one or two channels, the system may perform a safeshutdown for the process, if said disparity occurs in all channelsconcurrently.

A redundant computer system comprising a first channel, and a secondchannel, each channel comprising a primary processor; a secondaryprocessor, wherein said primary processor is in operative communicationwith said secondary processor; said primary and secondary processoroperate in parallel redundancy; said primary processor in the firstchannel and said primary processor in the second channel are inoperative communication with each other; said secondary processor in thefirst channel and said secondary processor in the second channel are inoperative communication with each other; an input module includes ineach channel a first and a second interface to provide operativecommunication of said input module with said primary and secondaryprocessor, said input module can be digital or analog module; said inputmodule in each channel is in operative communication with a first and asecond section of a dual redundant sensor (DRS) for each controlledpoint that deliver an input data to said input module; means in saidinput module for calculating a deviation between values of said inputdata produced by said first and in second section of the DRS for eachcontrolled point to indicate whether said deviation is withinpredetermined limits or not; said primary processor and said secondaryprocessor in each channel receive said input data for synchronouslyexecute an application program and for transfer an output data as aresult of said application program execution to an output module via afirst and a second interface; said output module can be digital oranalog; said output module in each channel includes an outputcontroller, said voter and improper sequence components, a logic circuitand a voting network; said output module can be digital or analog; saidvoter component is in operative communication with said PPM and saidSPM, said ISD component is in operative communication with said votercomponent and with said output controller; said comparison diagnostic insaid primary processor (PPM) and said secondary processor (SPM) in eachchannel for monitoring condition of said output module, said diagnosticincludes a voter component and includes an improper sequence detector(ISD) component; said comparison diagnostic allows the system fordisabling said output module if at least two elements among the PPM, theSPM, and the ISD vote that the output controller fails; means in saidimproper sequence detector that verify absence or presence a fault intimetable and verify consistency of program operations in an outputmodule, said output module in operative communication with said primaryprocessor and said secondary processor and with said ISD component; saidoutput controller connected via a read only bus with a neighboringoutput controller for receiving/sending said output data from/to saidneighboring output controller; means in said output controller foractivating a disparity signal on input of said logic circuit for somecontrolled points if the associated primary and secondary processorproduce said output data that are different due to occurrence oftransient faults, or due to said deviation that is out of saidpredetermined limits for said controlled points; said disparity signalis activated as a result of an Exclusive NOR (XNOR) operation betweensingle-bit output data that said output controller receives from theassociated PPM and SPM; the primary processor and the secondaryprocessor in each channel use said input data for synchronously executean application program and for transfer an output data as a result ofsaid application program execution to said output controller in saidoutput module; said logic circuit and voting network perform a logicoperation with said output data to provide 2-of-2 voting among outputdata produced by said first and second channel of the system, saidvoting network includes a fault recovery valve for each controlled pointto provide no single point of failure of said voting network; saidvoting networks includes plurality switches in series, said switches insaid first and second channels connected in parallel to provide outputof the system; the system performs said 2-of-2 voting even though onlytwo PPM or two SPM are operational; the system, thereby, continues to beoperational in the presence of any two faults in said PPM and said SPM;said output controller connected via a read only buses with neighboringoutput controller for receiving/sending said output data from/to saidneighboring output controller; said output controller excludes an ownoutput data from inputs of said logic circuit and uses output datareceiving from the neighboring output controller, the system thenperforms the 1-of-2 voting instead of 2-of-2 voting if said disparitysignal activates in said output controller for some controlled points;the system, thereby, continues operate in the presence of said disparityin one channel, the system may perform a safe shutdown for the process,if said disparity occurs in first and second channel concurrently; saidlogic circuit is in operative communication with said output controllerand in operative communication with said voting network, which containsmultiple switches in series for each controlled points, said switches insaid first and second channels connected in parallel; said logic circuitin said first channel provides outputs of the associated voting networkas a product of said output data received from said output controller insaid first channel and a sum of said output data receiving from outputcontrollers in said first and second channel; said logic circuit in saidsecond channel provides outputs of the associated voting network as aproduct of said output data received from said output controller in saidsecond channel and a sum of said output data receiving from outputcontrollers in said second and first channel.

A redundant computer system comprising a first channel, a second channeleach channel comprising a first central processor and a second centralprocessor that operate in parallel redundancy; said first centralprocessor is in operative communication with said secondary centralprocessor; a first input module and a second input module is inoperative communication with said first central processor and with saidsecond central processor via the associated interfaces; said first inputmodule and said second input module is coupled with a single sensor foreach controlled point for delivering an input data of the process to thefirst processor and to the second processor respectively; said first andsecond control processor use said input data for synchronously executean application program and for transfer an output data as a result ofsaid application program execution to said output module in normalsystem operation; said output module includes an output controller, avoter and an improper sequence components, a logic circuit, and a votingnetwork; said first output controller is in operative communication withsaid first central processor via said first interface and is inoperative communication with said second central processor via saidsecond interface; said second output controller is in operativecommunication with said second central processor via said firstinterface and is in operative communication with said first centralprocessor via said second interface; a first voter component and asecond voter component that is in operative communication with saidprimary central processor and with secondary central processor; animproper sequence detector that verify absence or presence a fault intimetable and verify a consistency of program operations of said outputcontroller; said output controller is in operative communication withthe associated logic circuit in said first and second channel; acomparing diagnostic in said first central processor (FCP) and saidsecond central processor (SCP) in each channel for monitoring conditionof said output module, said comparing diagnostic includes a votercomponent and includes an improper sequence detector (ISD) component;said comparison diagnostic allows the system for disabling said outputmodule if at least two elements among the FCP, the SCP, and the ISD votethat said output controller fails; said comparison diagnostic having nosingle point of failure allows the system to operate with one workingoutput controller in the event that neighboring output controller fails;said output controller connected via a read only bus with a neighboringoutput controller for receiving/sending said output data from/to saidneighboring output controller; said output controller activates adisparity signal on inputs of said logic circuit for some controlledpoints if said output controller receive different data from said firstand second control processor due to occurrence of some transient faults;said disparity signal is activated as a result of an Exclusive NOR(XNOR) operation between output data that said output controllerreceives from said first and second central processors;

said output data is substitutes by the output data produced byneighboring output controller for some controlled points if saiddisparity signal is activated for said controlled points; the systemcontinues operate if said disparity occurs in only one outputcontroller, the system performs a safe shutdown for the process, if saiddisparity occurs in output controllers in said first a second channelsconcurrently; said logic circuit is in operative communication with saidoutput controller and in operative communication with a voting network,which contains multiple switches in series; said switches in said firsta second channels connected in parallel for each controlled point; eachlogic circuit and each voting network receives said output data fromsaid first and second central processor via said output controller, saidlogic circuit and voting network perform a certain logic operation withsaid output data to provide said 2-of-2 voting among output data thatproduced by said first and second central processor; means in said firstand second central processor to use an additional separate buses thatprovide operative communication with both first and second outputcontrollers; said means provide the system continues to be operationalin the presence of two faults: in first control processor and in secondoutput controller, or in second central processor and in first outputcontroller; the system continues to be operational in the presence ofany single fault and may operate in the presence of some kind of twofaults; the system energizes controlled process in the fault freeoperation when both first and second central processor and associatingcomponents operating properly and de-energizes said process in thepresence of two dangerous failures in the system.

A computer system integrating safety and control functionalitycomprising a computer system integrating safety section and a controlsection that provide the system safety and control functionalityrespectively; a safety section includes at least one main chassishousing a first and a second channel, each channel comprising a firstcentral processor and a second central processor that operate inparallel redundancy; said first and second central processor are locatedin a main chassis, means in said first and second central processors forcommunicating with said control section and with an external devicesover separated buses in redundant configuration; said first and secondcentral processors are in operative communication through a redundantbus for synchronizing their operation; said first and second centralprocessor has at least one ETHERNET port and at least one ETHERNETswitch for operative communicating with one or multiple remote chassisvia a first and a second input/output controller located on said remotechassis; said remote chassis may be located far away from the mainchassis to be nearer to controlled process; said communicating arecooper or fiber cables or can be wireless; each said remote chassisincludes a first and a second input/output controller that is inoperative communication with said first central processor and with saidsecond central processor, a first and a second input module that is inoperative communication with said first and second input/outputcontroller,

said first input module and said second input module is coupled withsaid single sensor per controlled point for delivering an input data ofthe process to said first and second central processor respectively viathe associated input/output controllers (IOC); said first and secondcentral processor uses said input data for synchronously execute anapplication program and transfer said output data as a result of saidapplication program execution to said first and second IOC under normalsystem operation; said IOC, in turn, transfers said output data to saidoutput module that includes an output controller, said voter andimproper sequence components, a logic circuit, and a voting network;an improper sequence detector that verify absence or presence a fault intimetable and verify a consistency of program operations of said outputcontroller; the output controller is in operative communication with theassociated voter component and with the associated logic circuits insaid first and second channel; a diagnostic in said first centralprocessor (FCP) and said second central processor (SCP) in each channelfor monitoring condition of said output module, said diagnostic includesin each channel a voter component and includes an improper sequencedetector (ISD) component; said diagnostic allows the system fordisabling said output module if at least two elements among the FCP, theSCP, and the ISD vote that said output controller fails; said diagnostichaving no single point of failure allows the system to operate with oneworking output controller in the event that neighboring outputcontroller fails; a logic circuit is in operative communication withsaid output controller and in operative communication with said votingnetwork, which contains multiple switches in series; said switches indifferent voting networks connected in parallel for providing an outputof the system for each controlled point; said logic circuit and saidvoting network perform a certain logic operation with said output datato provide 2-of-2 voting among output data that said first and secondIOC receive from said first and second central processor; means in thefirst and second central processor for energizing the process in thefault free operation when two input/output controllers and allassociating modules and components operating properly and de-energizingsaid process in the presence of two dangerous failures in the system;said control section housing at least two process controllers arrangedin back-up redundant configuration, said process controllers performcontrol functions without interrupts from said safety section until acritical parameters of controlled process are in the safe range; saidcontrol section includes at least one main chassis housing a primary anda secondary process controller, that are in operative communication eachto other through a first and a second interface and a redundant bus;means in said first and secondary process controller for communicatingwith said safety section and with an external devices over separatedbuses; said primary and secondary central processor has at least oneETHERNET port and at least one ETHERNET switch for operativecommunicating with one or multiple remote chassis via the associatedinput/output controller located on said remote chassis; said remotechassis may be located far away from the main chassis to be nearer tocontrolled process; said communicating are cooper or fiber cables, orcan be wireless; each said remote chassis includes a multiple input andoutput modules that are in operative communicate with said first andsecond input/output controllers; said primary and secondary centralprocessor obtains an input data from said input modules via saidinput/output controllers and uses said input data for synchronouslyexecute an application program; means in said process controller toselect one process controller as a primary process controller, whileidentify the neighboring process controller as a secondary processcontroller; said first and second interface include a self-diagnosticand a mutual diagnostic for discovering possible faults occurrence insaid primary and in said secondary process controller respectively andfor disabling said first or second process controller when it fails;method in hardware and software in each process controller to use saidfirst and second interface for providing said process controller toobtain a primary status or a secondary status depends on location insaid backplane; select only said primary process controller for sendingoutput data as result of said control program execution to the systemcontrol outputs, for allowing said primary process controller to holdsaid primary status and operating in a stand-alone mode in the eventthat said neighboring process controller fails; said secondary processcontroller changes a secondary status to said primary status andperforms control function in said stand-alone mode in the event thatsaid primary process controller fails; said faulty process controllercan be online removing and replacing by a new process controller, statusof said new process controller is automatically setting up as a newstatus after inserting said new process controller into a backplane, andthen automatically changed from new status to secondary status during acurrent cycle of said control section operation; said new processcontroller is then reprogramming by the neighboring processor that holdssaid primary status; means in said primary and in secondary controllerto switch said serial interface from said self-diagnostic to an mutualdiagnostic by using a number of an electronic Single-Pole Double-Throw(SPDT) switches; means in said secondary process controller to changestatus from secondary status to primary status and starts operating insaid stand-alone mode if said primary process controller fails; means insaid primary process controller to keep primary status after going tosaid stand-alone mode in the event that secondary process controllerfails; said first and second interface in said primary and in secondaryprocess controller is for transmitting/receiving said self-diagnosticdata and said status to said primary and secondary process controllerrespectively.

A redundant control system of claim 5 wherein said primary and secondaryprocess controllers are identical; means in said process controllers fordefining said primary status or said secondary status after insertingsaid process controllers in said backplane and power up; said backplaneincludes a first socket connector located on the left side of saidbackplane and includes a second socket connector located on the rightside of said backplane; selected pins of said first socket connectorconnected to plus terminal of a power supply to form a firstidentification word, while selected pins of said second socket connectorconnected to ground terminal of said power supply to form a secondidentification word; a first and a second input port in each of saidprocess controllers, said input port coupled with a plug connector forinserting each process controller either to left side or to right sideof said backplane; if one said process controller inserted to left sideof said backplane it is coupled with a first socket connector, said oneprocess controller reads a first identification word via said firstinput port and gets said primary status after power up; if anotherprocess controller inserted to right side of said backplane it iscoupled with a second socket connector said another process controllerreads a second identification word via said second input port and getssaid secondary status after power up; said primary status and saidsecondary status of said process controllers are setting therebyinitially after system power up, but can be changed during systemoperation; said first and second interface is a serial peripheralinterface (SPI) in said primary and in secondary process controller fortransmitting/receiving said self-diagnostic data and status data to saidprimary and secondary process controller respectively; means in saidprimary and in secondary process controller to switch said SPI from saidself-diagnostic to an exchange said status data by using a number of anelectronic Single-Pole Double-Throw (SPDT) switches; further means insaid primary and in secondary process controller for continuouslyindicate primary or secondary status of said controllers; said primaryand secondary process controller can be remove and replace by newhealthy process controller if primary or secondary process controllerfails; status of said new healthy process controller is automaticallysetting up as new start status after power up, and then automaticallychanged to secondary status not later than during of one cycle of saidcontrol section operation; said SPI interfaces for discovering possiblefaults occurrence in the primary or in the secondary process controllerrespectively and disabling the primary or secondary process controllerwhen it fails; said SPI interfaces can operate in full Duplex mode.

BRIEF DESCRIPTION OF THE DRAWINGS

The various embodiments disclosed herein will become better understoodwith regard to the following description, accompanying drawings, andappended claims wherein:

FIG. 1 is a block diagram of one embodiment of a triple redundantcomputer system having channels A-C in accordance with the concepts anddisclosures presented herein;

FIG. 2 is a block diagram of the output modules of the triple redundantcomputer system shown in FIG. 1 in accordance with the concepts anddisclosures presented herein;

FIG. 3A is a schematic diagram of components of the output controller Aof the embodiment of FIG. 1 in accordance with the concepts anddisclosures presented herein;

FIG. 3B is a schematic diagram of components of the output controller Bof the embodiment of FIG. 1 in accordance with the concepts anddisclosures presented herein;

FIG. 3C is a schematic diagram of components of the output controller Cof the embodiment of FIG. 1 in accordance with the concepts anddisclosures presented herein;

FIG. 4 is a block diagram of another embodiment of the dual redundantcomputer system having channels A-B in accordance with the concepts anddisclosures presented herein;

FIG. 5 is a schematic diagram of two output modules of the embodimentsof FIG. 4 in accordance with the concepts and disclosures presentedherein;

FIG. 6A is a schematic diagram of the components of the channel A of thedual-doubled redundant computer system in accordance with the conceptsand disclosures presented herein;

FIG. 6B is a schematic diagram of the components of channel B ofdual-doubled redundant computer system in accordance with the conceptsand disclosures presented herein;

FIG. 7 is a block diagram of an embodiment of the dual redundantcomputer system in accordance with the concepts and disclosurespresented herein;

FIG. 8A is a schematic diagram of the components of channel A of thedual redundant computer system of the embodiment shown in FIG. 7 inaccordance with the concepts and disclosures presented herein;

FIG. 8B is a schematic diagram of the components of channel B of thedual redundant computer system of the embodiment shown in FIG. 7 inaccordance with the concepts and disclosures presented herein;

FIG. 9 is a block is a block diagram of an embodiment of the redundantcomputer system that integrates safety and control functionality inaccordance with the concepts and disclosures presented herein;

FIG. 9A is a schematic diagram of the components provided by the safetysection that are included in channel A of the redundant computer systemof the embodiment shown in FIG. 9 in accordance with the concepts anddisclosures presented herein;

FIG. 9B is a schematic diagram of the components of the safety sectionthat are included in channel B of the redundant computer system of theembodiment shown in FIG. 9 in accordance with the concepts anddisclosures presented herein;

FIG. 10 is a schematic diagram of a diagnostic system provided by thedual redundant control system shown in FIG. 9 in accordance with theconcepts and disclosures presented herein;

FIG. 11AA is a partial flow diagram showing the operation of the primarycontroller of the system provided in FIG. 9 in accordance with theconcepts and disclosures presented herein;

FIG. 11AB is another partial flow diagram showing the operation of theprimary controller of the system provided in FIG. 9 in accordance withthe concepts and disclosures presented herein;

FIG. 11AC is a further partial flow diagram showing the operation of theprimary controller of the system provided in FIG. 9 in accordance withthe concepts and disclosures presented herein;

FIG. 11BA is a partial flow diagram showing the operation of thesecondary controller of the system provided in FIG. 9 in accordance withthe concepts and disclosures presented herein;

FIG. 11BB is another partial flow diagram showing the operation of thesecondary controller of the system provided in FIG. 9 in accordance withthe concepts and disclosures presented herein; and

FIG. 11BC is a further partial flow diagram showing the operation of thesecondary controller of the system provided in FIG. 9 in accordance withthe concepts and disclosures presented herein.

DETAILED DESCRIPTION

In one embodiment, a redundant computer system 10 is shown in FIG. 1 ofthe drawings. The system 10 includes a plurality of parallel channels,and as such, may include for exemplary purposes, the following threechannels, identified as A, B and C. For clarity, the components of eachof the channels A, B and C are denoted in the drawings by respectivereference characters a, b and c. Furthermore, because each of theparallel channels A, B and C are structurally equivalent, only channel Ahas been discussed below. Channel A includes a primary processor module20 a (PPM A) and a secondary processor module 22 a (SPM A), whichoperatively communicate with each other via a communication bus 24 a.The interface 37-1 a of the output module A 44 a and the interface 38-1a of the input module A 49 a are in operative communication with the PPM20 a (PPM A) via an input/output (I/O) bus 12 a. In addition, theinterface 37-2 a of the output module A (44 a) and the interface 38-2 aof the input module A (49 a) are in operative communication with the SPM22 a (SPM A) via an input/output (I/O) bus 14 a. In some embodiments,the input and output modules and corresponding redundant sensors may bedigital or analog.

Thus, the PPM A receives input data from the input module A (49 a) viathe interface 38-1 a, and sends output data to the output module A (44a) via the interface 37-1 a. The SPM A receives input data from theinput module A via the interface 38-2 a, and sends output data to theoutput module A via the interface 37-2 a. In addition, an input module Ais provided in operative communication with a plurality of redundantsensors, such as dual redundant sensor (DRS) 51 a. It should beappreciated, that each sensor 51 a may integrate a first and a secondsection into a single hardware package, whereupon these sensors are usedfor the same measurement at each controlled point. The input module 49 asimultaneously obtains two values of input data that are issued by thefirst and second sections of one or more DRSs and sends them to PPM Aand to SPM B. A possible deviation may occur between the values of inputdata that is produced by the first and second sections of the DRS.

In addition, channel A, which has been described above, is in operativecommunication with channels B and C. As such, PPM A 20 a, PPM B 20 b andPPM C 20 c operatively communicate with each other via a primarycommunication bus 21, while SPM A 22 a, SPM B 22 b, and SPM C 22 coperatively communicate with each other via a secondary communicationbus 23. The primary communication bus 21 enables the PPM A-C tosynchronize their operation, while the secondary communication bus 23enables the SPM A-C to synchronize their operation. The bus 24 providesthe PPM and the associated SPM synchronous operation in each A-Cchannel. In addition, the output module A 44 a, the output module B 44 band the output module C 44 c operatively communicate with each other viaa communication bus 55, which in some embodiments may comprise aread-only bus.

In some embodiments, the system 10 performs safety and control functionson a cyclical basis, whereby an operation cycle period is defined by ascan time, which includes the time required for input data polling,application program execution, and a time required for the transfer ofoutput data to the output module. In addition, application programexecution and input data polling are overlapped. The PPMs A-C sendoutput data as result of the application program execution to theassociated output module 44, as shown in FIG. 2. The output controller40 in each channel compares the output data that it has received fromthe associated PPM and SPM, and uses the output data that is produced bythe PPM in the event that the associated SPM fails permanently.Similarly, the output controller 40 uses the output data that isproduced by the associated SPM if the associated PPM fails. In the eventthat the associated PPM and SPM are healthy, but the output controller40 discovers a disparity between the output data that produced by thePPM and SPM for a particular controlled point, it may be due to theoccurrence of an unacceptable data deviation or due to one or moretransient faults. The output data with disparity is counted as“doubtful”, and because of that, the output controller 40 activates adisparity signal D indicating that the system 10 is not utilizing thisdoubtful data. The output controller (OC) 40 then sends zero output datato the neighboring output controllers, and receives output data fromneighboring output controllers through the bus 55 to substitute thedoubtful output data. The output controller 40 a, for example, usesoutput data that is received from the PPM A by default, if the outputdata of the PPM A and SPM A do not have a disparity. The outputcontrollers in all channels operate similarly due to the symmetricalconfiguration of the components provided by the system 10.

Continuing to FIG. 2, the operational components of the output modulesA-C are presented. Specifically, the output module A includes outputcontroller A, logic circuit A, and voting network A; output module Bincludes output controller B, logic circuit B, and voting network B; andoutput module C includes output controller C, logic circuit C, andvoting network C. The output controller 40 a, for example, sends outputdata to the logic circuit 53 a, which is in operative communication withthe associated voting network via communication lines 54-1 a, 54-2 a,and 54-3 a for each controlled point.

The communication lines 54-1 a, 54-2 a, and 54-3 a connected to the anoptoelectronic isolation drivers 57-1 a, 57-1 b, and 57-1 c thatisolated logic circuits from switches 56-1 a, 56-2 a, and 56-3 a, thatare connected in series between the associated power supply V1 andoutput 63 a, which, in turn, are coupled with the load 66 of the system10. This configuration allows the system 10 performs two-out-of-three(2-of-3) voting among the output data A, B, and C during normaloperation and provides the system 10 to remain operational in thepresence up to any two faults. The comparison diagnostic, which isdescribed above is able to restore the system 10 back to properoperation after the occurrence of one or more permanent and transientfaults in each channel. In addition, the output controller uses anysuitable technique, such as SEC-DED (single error correct, double errordetect), which allows for the correction of any one fault, and toindicate the occurrence of two faults in the PPM and SPM during theircommunication with the output controller through the associated buses 12and 14.

Furthermore, the system 10 continues to perform 2-of-3 voting if allthree PPMs or all three SPMs in different channels are failingconcurrently, since each channel still produces three sets of outputdata that are received either from PPMs A-C or from the SPMs A-C. Thesystem 10, therefore, provides a high level of fault tolerance withrespect to permanent faults, which may occur in the PPMs A-C or in theSPMs A-C.

In another embodiment, the system 10 may be configured to utilize asingle triple redundant sensor (TRS) that includes three identicalsections that are integrated in a single hardware package. The sectionsof the TRS are designed to measure a value of a single controlled pointin the process. The sections S1, S2, and S3 are coupled with inputmodules 49 a, 49 b, and 49 c respectively. The input module 49 areceives input data from sensor S1, and transfers this data in a digitalformat to the PPM A and SPM A simultaneously through buses 12 a and 14a. The input module 49 b receives the input data from sensor S2 andtransfers it in a digital format to the PPM B and the SPM Bsimultaneously through buses 12 b and 14 b. In addition, the inputmodule 49 c receives input data from sensor S3 and transfers it in adigital format to the PPM C and SPM C simultaneously through buses 12 cand 14 c. It should be appreciated that in some embodiments, the inputmodules 49 may be digital or analog. The PPM and the SPM in each channelreceive input data, execute an application program and transfer outputdata in single-bit format to output module 44 that also can be digitalor analog. The output controller 40, the logic circuit 53, and thevoting network 54 provide output 61 as result of 2-of-3 voting amongoutput data A, B, and C if the system 10 operates with digital modules,as it was described above. Alternatively, if the system operates withanalog modules, then an analog module in each channel utilizes saidoutput controller that is coupled with a digital-to-analog converter(DAC). The outputs of the DAC in each channel may be coupled with aconventional current summing circuit (CSC), which provides output 61 ofthe system 10 as a mid-value among the output currents that are producedby all of the channels of the system 10. The current summing circuit isable to keep the same value of output current in the event that up totwo channels concurrently fail. (Analog output modules are not shown inFIG. 2 for the sake simplicity). A Triple Redundant (TMR) diagnosticusing a digital or analog module includes a 2-of-3 voter 31 that iscoupled with an improper sequence detector (ISD) 33, and is coupled withan associated PPM and SPM in each channel. The operation of such systemswill be clear from the description presented below.

Continuing, the output module A includes an output controller A 40 a anda logic circuit A. The output controller A includes interfaces 37-1 aand 37-2 a, as previously discussed. In addition, the output controllerA (OC A) sends output data A to output controllers B and C, and receivesoutput data B and C from them at the same time via bus 55. Outputcontroller A operatively sends data A to the logic circuit A and issuessignals Sa, Da, and inverted signal (Da)′ on the corresponding inputs ofthis logic circuit. The output data produced by PPM A and SPM A isdesignated herein as A1 and A2. The output controller calculates a “D”signal for each controlled point in channel A using the followingequation: D={XNOR with A1, A2}, where Da is equal to ‘1’, if there is nodisparity between data A1 and data A2. If a disparity exists betweendata A1 and data A2, then the output controller 40 sets the inversesignals (Da)′ that is equal to “0”. A truth table is shown in Table 1below.

TABLE 1 A1 A2 XNOR Da Da′ 0 0 1 1 0 1 1 1 1 0 1 0 0 0 1 0 1 0 0 1

As shown in Table 2 below, Da signals are set to a ‘1’ state forcontrolled points 0, 1, 2, and 3 for which output data of PPM A and SPMA are equal, and Da signal is set to a ‘0’ state for 4, 5, 6, and 7controlled points.

TABLE 2 PPM A SPM A Da (Da′) Points data data signal signal 0 1 1 1 0 10 0 1 0 2 1 1 1 0 3 0 0 1 0 4 1 0 0 1 5 0 1 0 1 6 1 0 0 1 7 0 1 0 1

The PPM A 20 a is in operative communication with a voter component 31 aby a communication line 25 a, and the SPM 22 a is in operativecommunication with the voter component 31 a by a communication line 27a. The voter component 31 a may be, in some embodiments, a 2-out-of-3voter component. An improper sequence detector (ISD) module 33 a is inoperative communication with the voter component 31 a. The ISD 33 amonitors both time-based programs and logical programs that the outputcontroller 40 a executes. In the event that the ISD 33 a discovers thatthe output controller 40 a has failed, the ISD 33 a activates an outputsignal 28 a. The PPM A uses line 25 a to activate an alarm signal when afailure in the output controller 40 a is discovered during communicationbetween PPM A and the output module 40 a. Similarly, the SPM A uses line27 a for activating an alarm signal when a failure in the outputcontroller 40 a is discovered during communication between SPM A and theoutput controller 40 a. If the ISD 33 a discovers the occurrence of afailure in the output controller 40 a, the ISD 33 a activates an alarmsignal on output 28 a. The voter component 31 a then produces outputsignal 36 a, as result of two-out-of-three (2-out-of-3) voting among thealarm signals that are produced by the PPM A, the SPM A, and the ISD 33a. Output signal 36 is also used to disconnect the output 63 a from theoutput 61 of the system 10 in the event of a fault occurrence in theoutput controller 40 a. The performance of this diagnostic in eachchannel allows the system 10 to discover one or more possible failuresin the output controller 40, since the voter component has no singlepoint of failure, as will be discussed in detail below.

FIGS. 3A-C present the details of how the components of the outputmodule 44 a-c operate. The TMR diagnostic include a 2-of-3 voter 31 thatis coupled with an improper sequence detector (ISD) 33 and is coupledwith an associated PPM and SPM in each channel. As previously discussed,the output controller A is in operative communication with the ISD 33 a,which is in operative communication with the voter component 31 a. Inaddition, the voter component 31 a is in operative communication witheach of the logic circuits A, B and C via line 36 (Wa). The votercomponent 31 a includes a plurality of parallel voting groups 39-1 a,39-2 a, and 39-3 a, which are coupled between a voltage source A and aresistor 29 a, which is connected to the ground node. Each group 39 aincludes two electronic switches, such as MOSFET switches, othertransistors or relays that are connected in series. A first switch ofgroup 39-1 a and a second switch of group 39-2 a are coupled tocommunication line 25 a, which are controlled by the PPM A. A firstswitch of group 39-3 a and a second switch of group 39-1 a are coupledto line 27 a, which are controlled by the SPM A. A first switch of group39-2 a and a second switch of group 39-3 a are coupled to line 28 a,which are controlled by the ISD 33 a. The voter component A thereforereceives three input signals from the PPM A, the SPM A, and the ISD A,and produces output signal 36 a (Wa) as result of a majority oftwo-out-of-three voting among signals from PPM A, SPM A, and ISD 33 a.The output 36 a (Wa) of the voter component 31 a is coupled to the logiccircuit A and is coupled to logic circuits B and C. The voter componentB and C are identical to voter component A, and as such, has a similarconnection with PPM b-c, SPM b-c, and ISD 33 b-c due to the symmetricalconfiguration of the system 10. As such, the voter 31 a-c configurationprovides 2-of-3 voting and enables the system 10 to operate in thepresence of any single failure.

It should be appreciated, that the TMR diagnostic described above allowsthe system to operate with one working output controller 40 in the eventthat the other output controllers 40 of the other channel fail. Suchoperation of TMR diagnostic that has no single point of failure ensuresthat fault occurrences in the associated output controller areidentified.

In addition, current/voltage sensors 59 are shown in FIGS. 3 A-C, whichare used to verify a value of electrical current passing through theswitches 56 a-c, and are able to determine a value of a voltage across aload 66. In addition, a feedback line 60 a allows a controller 40 a tomonitor the load 66 state and the condition of switches 56 a. It shouldbe appreciated that all connections described above with the respect tothe output controller A, the logic circuit A, and the voting network Aare similar and applicable for controllers B (FIG. 3B) and C (FIG. 3C)due to the symmetrical configuration of the system 10. Because of this,the output 36 b (Wb) of the voter component 31 b is coupled to the logiccircuit B and is coupled to the logic circuits A and C. The output 36 c(Wc) of the voter component 31 c is coupled to the logic circuit C andis also coupled to the logic circuits A and B.

Logic circuit 53 a (FIG. 3A) includes logic elements G1-G12, where theoutputs of G10, G11, and G12 are inverted by the isolation drivers 57-1a, 57-2 a, and 57-3 a that are respectively coupled with power switches56-1 a, 56-2 a, and 56-3 a that are located on the voting network 54 a.It should be appreciated that each isolation driver 57 may include anoptoelectronic isolation driver; however, the isolation driver 57 maycomprise any suitable device. It should also be appreciated that theswitches 56-1 a, 56-2 a, and 56-3 a may comprise MOSFET powertransistors, as shown, or any other controllable switches.

The logic circuit 53 a and the voting network 54 a operate, as shown inFIG. 3A, whereby the identifier (′) indicates that it is an inversevalue. Accordingly, the output of logic gate G8 is given as:

Â(Wb+Wc)′+B̂Wb+ĈWc=X1a, which is defined as X1a for simplicity.

The expression [(Wb)′]̂[(Wc)′]=(Wb+Wc)′ in X1 a is coupled to inputs G1,G3, and G12. On the inputs of G1, occur signals A and X1 a, whereby theoutput of G1 produces signal ÂX1 a. The output controller A (OC A) setsa logical signal Da=‘1’ and sets its inverse signal (Da)′=‘0’ on thefirst inputs of G2 and G3 respectively when there are no disparitiesbetween data output by PPM A and SPM A. The output controller A (OC A)sets a logical signal Da=‘0’ and sets its inverse signal (Da)′=‘1’ onthe first inputs of G2 and G3, respectively, in the event that adisparity exists between the data output by PPM A and SPM A. Signal X1 aoccurs on the second inputs of G1 and G3, while signal ÂX1 a occurs onthe second input of G2. The output of G2 then produces signal (ÂX1 âDa)′, while the output of G3 produces signal [X1 â(Da)′]′. As aresult, G4 produces a signal [(ÂX1 âDa)′]̂[X1 â(Da)′]′=Y1 a, that isidentified as Y1 a for simplicity. The output of gate 4 is given by thelogic expression:

Y1a={[(ÂX1âDa)′]̂[(X1â(Da)′]′}′=[(ÂX1a)′]′ since Da=‘1’, (Da)′=‘0’ innormal operation of the system 10.

Signals Wb and Wc are normally in a ‘1’ state, and because of that(Wb+Wc)′=‘0’, hence X1 a=B+C, Y1 a=[Â(B+C)]′=‘1’ for each controlledpoint under normal operation. Data Y1 a on output G4 is inverted twice:first Y1 a is inverted to ‘0’ by gate G11 that provides a ‘0’ input forthe isolated driver 57-2 a; and the output of driver 57-2 a is secondlyinverted to a ‘1’ on input S-2 a, which forces switch 56-2 a to be in anON state.

The output of G8 is equal to: X1 a=Â(Wb+Wc)′+B̂Wb+ĈWc=‘0’+B+C=B+C. Inaddition, signal X1 a is coupled with one input of gate G12, anotherinput of which is coupled with signal Wa. The gate 12 output signal isdefined as Y2 a=(X1 âWa)′. When the system 10 in an energized state,signal X1 a=‘1’ and signal Wa=‘1’; whereupon gate 12 gives an outputsignal (X1 âWa)′=‘0’. The isolation driver 57-3 a, in turn, invertssignal ‘0’ to provide a ‘1’ signal on output S3-a, which is coupled witha control input of the MOSFET power switch 56-3 a. The output of G8 is,thereby, inverted twice and it is transformed to signal S-3 a=‘1’ thatforces switch 56-3 a to be in an ON state. As a result, MOSFET switches56-3 a are also is placed into an ON state. In addition, the outputcontroller 40 a, during normal operation, sets signal Sa=‘1’ andproduces signal (SâWa)′=‘0’ on the output of the gate 10. The isolationdriver 57-1 a, in turn, inverts this signal ‘0’ to set a ‘1’ signal onthe output S1-a, which is coupled with control input of a fault recoveryvalve (FRV) 56-1 a, which, in turn, goes to an “ON” state during normaloperation of the system 10. It should be appreciated, that the faultrecovery gate A may also comprise a MOSFET power switch or any othersuitable transistor. All power switches 56-1 a, 56-2 a, and 56-3 a,therefore, will be in an “ON” state so that the output 63 a is normallyenergized. The FRVs A-C are used to disconnect the output 63 a-c fromthe system output 61 in the event of a fault occurrence in channels A-C.

Output 63 a for each controlled point is defined as a logical productthat provides switches 56-1 a, 56-2 a, and 56-3 with the correspondingsignals S-1 a, S-2 a, and S-3 a, which, in turn, are controlled by theoutputs 54-1 a, 54-2 a, and 54-3 a of the logic circuit 53 a. Thus,output 63 a is equal to: [Â(B+C)]̂(B+C)=Â(B+C).

If a majority of the dual redundant sensors issue one or more signalsthat go out of a safe range, the controlled process may be in dangerouscondition. In that event, the PPM A 20 and SPM 22 in each channel A-Cmay produce output data A=B=C=‘0’ for each affected point in thecontrolled process. The logic circuits 53 a, for example, receive signalA=‘0’ and receives signal X1 a=‘0’ from the PPM A 20 a via thecorresponding output controller 40 a. Logic circuit 53 a then providessignal Y1 a=‘0’ at the input of gate G11, which inverts signal Y1 a to‘1’ at output 54-2 a. The isolated driver 57-2 a, in turn, invertssignal ‘1’ to ‘0’ on the output S2-a, which drives the power MOSFETswitch 56-2 a to an “OFF” state. Gate 12 then provides output signal (X1âWa)′=‘1’, since signal X1 a=‘0’. The isolation driver 57-3 a, in turn,inverts input signal ‘0’ to provide a ‘1’ signal on the output S3-a,which is coupled with control input of the power MOSFET switches 56-3 a.As a result, MOSFET 56-3 a goes to an “OFF” state. Similarly, MOSFETswitches 56-2 b and 56-3 b are driven to an “OFF” state. When the powerswitches 56-1 a, 56-2 a, and 56-3 a are in an “OFF” state, the switches56-1 b, 56-2 b, and 56-3 b and the power switches 56-1 c, 56-2 c, and56-3 c are also placed in an “OFF” state as well; and the controlledprocess will be de-energized from the output 61 and the load 66. Thesystem 10, therefore, brings the controlled process to a safe conditionby such shutdown process.

It should be appreciated that all of the elements and their connectionsdescribed above with the respect of the output controller A, logiccircuit A, and voting network A are similar and applicable for use incontrollers B in channel B (FIG. 3B) and controllers C in channel C(FIG. 3C) due to the symmetrical configuration of the system 10.

Continuing, the following expressions for outputs 63 b and 63 c areprovided as: Output 63 b=B̂(A+C); and Output 63 c=Ĉ(A+B). The output 61of system 10 is given as a logical sum of outputs 63 a, 63 b, and 63 csince they are coupled in parallel:

Output 61=Â(B+C)+B̂(A+C)+Ĉ(A+B).  (1)

Continuing, the following expressions for outputs 63 b and 63 c areprovided as: Output 63 b=B̂(A+C), and Output 63 c=Ĉ(A+B). The output 61of the system 10 is given as a logical sum of outputs 63 a, 63 b and 63c since they are coupled in parallel: Output 61=Â(B+C)+B̂(A ̂C) Ĉ(A+B).Thus, the system 10 performs 2-of-3 majority voting among data A, B andC during normal operation.

The impact of a possible fault occurrence in the output controllers 40,logic circuits 53, and the voting networks 54 is considered below. Theexpression (1) is transformed to logic expression (2) in which allsignals are counted:

$\begin{matrix}{{{Output}\mspace{14mu} 61} = {{{{Output}\mspace{14mu} {A\left( {63\; a} \right)}} + {{Output}\mspace{14mu} {B\left( {63b} \right)}} + {{Output}\mspace{14mu} {C\left( {63c} \right)}}}=={{{{SaAWa}\left\lbrack {{BWb} + {CWc} + {A\left( {{Wb} + {Wc}} \right)}^{\prime}} \right\rbrack}{Da}} + {{{SaWa}\left\lbrack {{BWb} + {CWc} + {A\left( {{Wb} + {Wc}} \right)}^{\prime}} \right\rbrack}({Da})^{\prime}} + {{{SbBWb}\left\lbrack {{AWa} + {CWc} + {B\left( {{Wa} + {Wc}} \right)}^{\prime}} \right\rbrack}{Db}} + {{{SbWb}\left\lbrack {{AWa} + {CWc} + {B\left( {{Wa} + {Wc}} \right)}^{\prime}} \right\rbrack}({Db})^{\prime}} + {{{ScCWc}\left\lbrack {{AWa} + {BWb} + {C\left( {{Wa} + {Wb}} \right)}^{\prime}} \right\rbrack}{Dc}} + {{{ScWc}\left\lbrack {{AWa} + {BWb} + {C\left( {{Wa} + {Wb}} \right)}^{\prime}} \right\rbrack}{({Dc})^{\prime}.}}}}} & (2)\end{matrix}$

It is clear, that the expression (2) is transformed to expression (1) ifWa=Wb=Wc=1; Da=‘1’, (Da)′=‘0’; Sa=Sb=Sc=‘1’, which takes place in normaloperation.

The following discussion presents the impact that the occurrence offaults in the logic circuit 53 a and in the output voting network 54 ahave on the system. Furthermore, any possible faults and their affect tothe operation of the system 10 may be obtained by using the expression(2). For example, when the output controller 40 a receives output datafrom the PPM A and the SPM A and a disparity exists between their datafor some points, the output controller 40 a counts this data asundefined and sets a logical “Low” state for the output data A on theinputs of the neighboring output controllers 40 b-c for these points.The output controller 40 a also sets disparity signal Da to a ‘0’ stateand signal (Da)′ to a ‘1’ state for these points. As a result,expression (1) is provided as follows:

Output A=(B+C+‘0’)=B+C, since A=‘0’; Wa=Wb=Wc=‘1’; Sa=‘1’; Da=‘0’; and(Da)′=‘1’;

Output B=B(‘0’+C+‘0’)=BC, since A=‘0’; Wa=Wb=Wc=‘1’; Sb=‘1’, Db=‘1’; and(Da)′=‘0’;

Output C=C(‘0’+B+‘0’)=BC, since A=‘0’; Wa=Wb=Wc=‘1’, Sc=‘1’, Dc=‘1’; and(Dc)′=‘0’.

Thus, output 61 becomes equal (B+C)+BC+BC=B+C.In this example, output data of channel A for some controlled points aredoubtful and they are substituted by the output data that channel A hasreceived from neighboring channels B and C. The system, however,performs 2-of-2 voting for points with a disparity instead of 2-of-3voting.

In the event that channel A and channel B have different output data,expression (2) is set forth as follows:

Output 63 a=(‘0’+C+‘0’)=C, since A=B=‘0’; Wa=Wb=Wc=‘1’; Sa=‘1’; Da=‘0’;and (Da)′=‘1’;

Output 63 b=(‘0’+C+‘0’)=C, since A=B=‘0’; Wa=Wb=Wc=‘1’; Sb=‘1’, Db=‘0’;and (Db)′=‘1’;

Output 63 c=(‘0’+‘0’+‘0’)=0, since A=B=C=‘0’; Wa=Wb=Wc=‘1’, Sc=‘1’,Dc=‘1’; and (Dc)′=‘0’.

Thus, the system output (SO) 61 becomes equal, such that SO=C+C=C. Ifchannels A and B concurrently fail and the output data has a disparityfor points that are safety-critical, this output data is substituted bythe output data that channel A and channel B receive from channel C.Thus, for this data, the system 10 performs 1-of-1 voting, but continuesto be operational in the presence of multiple faults. If three outputcontrollers concurrently discover a disparity in the output data forsome points, the system 10 initiates a shutdown of the process byde-energizing the system output 61 and passing the process to a safestate.

In the event that two logic circuits 53 in different channels fail in away that the associated electronic switches 56 (e.g. transistors orrelays) are in a permanently “OFF” state for some controlled points,outputs 63 of the associated channels are de-energized for these points,but the system 10 still remains operational by using the third healthychannel. If switches 56-2 and 56-3 in the associated channel fail beingpermanently in the “ON” state the dangerous failure of the system mayoccur. The output controller 40 a-c in the associated channel activatessignal Sa-c on the input of gate G10 of the associated logic circuit 53,which, in turn, sets the associated fault recovery switch 56-1 to be inan “OFF” state. Because of that outputs 63 of the associated channel isde-energized to avoid this dangerous situation. The system 10, however,remains operational by means of the two healthy channels. In the eventthat two logic circuits 53 concurrently fail holding the two associatedswitches 56-2 and 56-3 in an “ON” state or in an “OFF” statepermanently, the system also remains operational. Consequently, thesystem 10 remains operational by means of the single healthy channel inthe presence of multiple faults in two neighboring channels. Inaddition, the system performs a shutdown process that passes the processinto a safety condition if all channels A-C concurrently fail.

In some embodiments, the system utilizes three identical power suppliesfor providing power to channels A-C. Each power supply includes thenecessary components to detect the occurrence of faults within the powersupply itself and for preventing fault penetration to the power suppliesof the other channels A-C. This allows the system 10 to continue to beoperational if at least one power supply out of the three remainshealthy. Thus, the system 10 disclosed herein is capable of operating inthe presence of up to two transient or permanent faults in anycombination of the system's components.

Moreover, the system 10 uses diverse redundancy as a protection againsta common cause failure. Each PPM uses same hardware and same software,which are different with hardware and software that each SPM uses. Thisallows the system 10 to eliminate a common cause failure that is theresult of software design errors or hardware faults. An alternativeapproach for decreasing the probability of common cause failures is touse a functional block diagram (FBD) language for developing the sameapplication program for each the associated PPM and SPM. The applicationprogram may be divided into segments, with each segment being executedwithin one scan period, and with the segments being executed in theorder that is defined by a user's algorithm. This approach allows thesystem to use the same software and hardware for the primary andsecondary processor modules, and significantly decreases the probabilityof a common failure. Furthermore, utilizing this approach in channel A-Cprovides the system 10 with the ability to replace faulty primary orfaulty secondary processor modules with a new processor module. Thehealthy processor module can then reprogram the new processor modulesince both the processor modules have the same software and hardware.

The system 10 is configured to use a comparison diagnostic that iscombined with voting techniques that allow the system to remainoperational upon the occurrence of multiple faults within the primaryand secondary processor modules. In addition, the system 10 is able tobe operational on the occurrence of up to two faults within the I/Omodules and may operate properly upon the occurrence of some type ofthree faults. The system 10 is also able to detect a possible disparityin output data, and continues to remain operational upon the occurrenceof two faults caused by the disparity. This system includes a veryeffective fault diagnostic that has no single point of failure andallows the system to operate properly upon the occurrence of up to twofaults and upon the occurrence of some types of three faults. The system10 also provides diverse redundancy that significantly reduces theprobability of common cause failures. In addition, the system 10 alsoutilizes I/O (input/output) circuits with a reduced number of internalelements, thereby allowing lower system cost to be achieved. Thearchitecture of the system 10 allows it to be manufactured to producedifferent m-out-of-n redundant computer systems by reprogramming only afew elements, such as the logic circuit for example, if it isimplemented as a single-chip, such as a field programmable gate array(FPGA) or an application specific integrated circuit (ASIC) for example.The m-out-of-n systems, such as those disclosed herein include only adifferent number of the same elements.

In another embodiment, as shown in FIGS. 4 and 5, a dual duplicatedsystem (DDS), is referred to by numeral 11, which includes two channelsthat are similar to the channels in the URS (ultra-reliable computingsystem) system 10 described above. The DDS system 11 operates similarlyas the URS system 10 discussed above, with the DDS system 11 having thesame elements that the URS system 10 utilizes, but with the number ofelements being 1.5 times less than in the URS system. Thus, the DDSsystem 11 is substantially less expensive in comparison with the URSsystem 10. As such, channel A and channel B of the DDS system 11 areequivalent to respective channel A and channel B of the URS system 10.As such, each channel A and B of the DDS system 11 includes respectiveoutput modules A and B, as shown in FIG. 4, which are structurallyequivalent to the output modules A and B shown in FIG. 2 of the URSsystem 10. Each of the output modules A and B include the TMR diagnosticsystem that includes a 2-of-3 voter component 31 and the impropersequence detector component 33. The DDS A includes logic circuit 67 thatis substantially similar to the logic circuit 53 described above.

The output modules A and B of the DDS system 11 are structurallyequivalent to the output modules A and B of the URS system 10, such thatthe DDS system 11 in the channel A includes the primary processor module20 a (PPM A) and the secondary processor module 22 a (SPM A). Inaddition, channel A includes the output controller 40 a, the logiccircuit 67 a, and the voter network 54 a. Channel B includes the primaryprocessor module 20 b (PPM B) and the secondary processor module 22 b(SPM B). Additionally, channel B includes the output controller 40 b,the logic circuit 67 b, and the voter network 54 b. Channel A includes aprimary processor module 20 a (PPM A) and a secondary processor module22 a (SPM A), which operatively communicate with each other via acommunication bus 24 a. The interfaces 37-1 a and 37-2 a of outputmodule A 44 a and the interfaces 38-a and 38-2 a of input module A 49 aare in operative communication with the PPM 20 a and SPM B 22 a via aninput/output (I/O) bus 12 a and 14 a respectively. The interfaces 37-1 band 37-2 b of the output module 44 b and the interfaces 38-1 b and 38-2b of the input modules A 49 b are in operative communication with thePPM 20 b and SPM B 22 b via an input/output (I/O) bus 12 b and 14 brespectively.

It should be appreciated that the input and output (I/O) circuits can bedigital or analog, however, with regard to the discussion herein,digital I/O modules are utilized. Furthermore, input module 49 a-boperatively communicates with dual redundant sensors 51 a-b forreceiving process information. Each sensor 51 a may be integrated into asingle hardware package, whereupon a first and a second section of dualredundant sensors (DRS) 51 a are utilized to conduct the samemeasurement for each controlled point. For example, the PPM A receivesinput data that is produced by the first section through bus 12 a, whilethe SPM A receives input data that is produced by the second sectionthrough bus 14 a. A possible deviation can occur between the values ofthe input data that is produced by the first and second sections of theDRS.

In some embodiments, the system 11 performs safety and control functionson a cyclical basis, whereby an operation cycle period is defined by ascan time, which includes the time required for input data polling,application program execution, and the time required for the transfer ofoutput data to the output module. In addition, application programexecution and input data polling are overlapped.

The PPMs A-B send the output data as result of the application programexecution to the associated output controller 40, as shown in FIG. 5.The output controller 40 in each channel compares the output data thatit has received from the associated PPM and SPM, and uses the outputdata that is produced by the PPM in the event that the associated SPMfails permanently. Similarly, the output controller 40 uses the outputdata that is produced by the associated SPM if the associated PPM fails.The output controller 40 uses the output data that is received from theassociated PPM by default, if both PPM and SPM are healthy and do nothave a disparity, that can occur because of the possible unacceptabledeviation between the values of input data that are produced by thefirst and second sections of the DRS. In the event that the associatedPPM and SPM are healthy, but the output controller 40 discovers adisparity between the output data that produced by the PPM and SPM for aparticular controlled point, it may be due to the occurrence ofunacceptable deviations or due to one or more transient faults. Theoutput data with a disparity is counted as “doubtful”, and because ofthat, the output controller 40 activates a disparity signal D indicatingthat the system 11 is not utilizing this doubtful data. The outputcontroller (OC) 40 then sends zero output data to the neighboring outputcontroller, and receives output data from neighboring output controllerthrough the bus 65 to substitute the doubtful output data. The outputcontrollers in all channels operate similarly due to the symmetricalconfiguration of the components provided by the system 11.

FIG. 5 presents the operational components of the output modules A and B(44 a-b). As such, the output module A includes the output controller A,the logic circuit A, and the voting network A; output module B includes:the output controller B, the logic circuit B, and the voting network B.

The output controller 40 a receives the output data produced by the PPMA and SPM A via interfaces 37-1 a and 37-2 a respectively; the outputcontroller 40 b receives the output data produced by the PPM B and SPM Bvia interfaces 37-1 b and 37-2 b respectively. In addition, the outputcontroller A is able to operatively communicate with the outputcontroller B via the communication bus 65. In some embodiments, thecommunication bus comprises a read-only bus. As such, the communicationbus 65 enables each of the output controller 40 a-b to communicate withone or more of the other output controllers, such as by sending and/orreceiving output data. The isolation driver 57 is used to provideisolation of a logic section of the system 11 from its power section. Itshould be appreciated that the isolation driver 57 may comprise anoptoelectronic isolation driver; however, any isolation driver 57 maycomprise any suitable device.

Each output controller 40 includes a windowed timer that verifies thatthe associated PPM and SPM delivers output data to the output controlleron time. If, for example, the PPM A or SPM A fails to deliver the outputdata on time, the output controller 40 a indicates a failure occurrencein one or the PPM A/SPM A or in both of them. The output controller 40in each channel compares the output data that it has received from theassociated PPM and SPM, and uses the output data that is produced by thePPM in the event that the associated SPM fails permanently. Similarly,the output controller 40 uses the output data that is produced by theassociated SPM if the associated PPM fails. The output controller 40 bydefault uses the output data that is received from the PPM if the outputdata of the associated PPM and SPM do not have a disparity. In the eventthat an associated PPM and SPM are healthy, but the output controller 40discovers a disparity between output data produced by the associated PPMand SPM for some controlled points, it may be due to unacceptabledeviation or due to occurrence of transient faults. The output data withdisparity is counted as “doubtful” and is not used in the channel withthe disparity. Accordingly, the output controller 40 activates disparitysignal D so that the system 11 does not use these doubtful data. Inaddition, the output controller 40 then sends a zero output data to theneighboring output controller, and receives output data from theneighboring output controller through bus 65. The output data receivedfrom neighboring output controller is then used for substituting thedoubtful output data.

Continuing, the output controller A operatively sends single-bit data Ato the logic circuit A (67 a) and issues disparity signal Da, invertedsignal (Da)′, and signal Sa, and on the corresponding inputs of thislogic circuit. Output data are identified as A1 and A2, which the outputcontroller 40 a receives from PPM A and SPM A respectively. The outputcontroller 40 a calculates disparity signal D for each controlled pointusing the following equation: D={XNOR with A1, A2}, where Da is equal to1 ‘ if there is no disparity between data A1 and data A2. If a disparityexists between data A1 and data A2, then the output controller 40 setsinverse signal (Da)’ equal to ‘0’. A truth table is shown in Table 3below.

TABLE 3 A1 A2 XNOR Da Da′ 0 0 1 1 0 1 1 1 1 0 1 0 0 0 1 0 1 0 0 1

As shown in Table 4 below, disparity signal Da are set to a logical ‘1’state for points 0, 1, 2, and 3 for which PPM A and SPM A output dataare equal and setting signal Da to a logical ‘0’ state for 4, 5, 6, and7 points.

TABLE 4 PPM A SPM A Da (Da)′ points data data signal signal 0 1 1 1 0 10 0 1 0 2 1 1 1 0 3 0 0 1 0 4 1 0 0 1 5 0 1 0 1 6 1 0 0 1 7 0 1 0 1

The comparison diagnostic that is described above is able to recoverfrom many permanent and transient faults that may occur in each channel.In addition, the output controller uses any suitable technique, such asSEC-DED, which allows for the correction of any transient fault, and toindicate the occurrence of two faults in the PPM and SPM during theircommunication with the output controller through the associated buses 12and 14.

The TMR diagnostic includes a 2-of-3 voter component 31 that is coupledwith an improper sequence detector (ISD) 33 and is coupled with anassociated PPM A and SPM in each channel. Output 35 a of the outputcontroller A, as shown in FIG. 6A, connected with input of the impropersequence detector (ISD) 33 a. The ISD 33 a monitors both time-basedprograms and logical programs that the output controller 40 a executes.In the event that the ISD 33 a discovers that the output controller 40 ahas failed, the ISD 33 a activates an output signal 28 a.

The PPM A uses line 25 a to activate an alarm signal when a failure inthe output controller 40 a is discovered during communication betweenPPM A and the output module 40 a. Similarly, the SPM A uses line 27 afor activating an alarm signal when a failure in the output controller40 a is discovered during communication between SPM A and the outputcontroller 40 a. The voter component 31 a then produces output signal 36a, as result of two-out-of-three (2-out-of-3) voting among the alarmsignals that are produced by the PPM A, the SPM A, and the ISD 33 a.Output signal 36 a is also used to disconnect the output 63 a from theoutput 61 of the system 11 in the event of a fault occurrence in theoutput controller 40 a. Similarly, output signal 36 b is used todisconnect the output 63 b from the output 61 of the system 11 in theevent of a fault occurrence in the output controller 40 b. Theperformance of this diagnostic in each channel allows the system 11 todiscover one or more possible failures in the output controller 40,since the voter component has no single point of failure, as will bediscussed in detail below. In addition, the voter component 31 a is inoperative communication with each of the logic circuits A and B viacommunication line Wa. The voter component 31 a, which may be a 2-of-3voter component includes a plurality of parallel voting groups 39-1 a,39-2 a, and 39-3 a, which are coupled between a voltage source A and aresistor 29 a, which is connected to a ground node as shown in FIG. 6a .Each group 39 a includes two electronic switches, such as transistors orrelays for example, which are connected in series. A first switch ofgroup 39-1 a and a second switch of group 39-2 a are coupled to line 25a, that are controlled by PPM A. A first switch of group 39-3 a and asecond switch of group 39-1 a are coupled to line 27 a, that arecontrolled by SPM A. A first switch of group 39-2 a and a second switchof group 39-3 a are coupled to line 28 a, which are controlled by ISD 33a. The voter component A, therefore, receives three input signals fromPPM A, SPM A, and ISD A, and produces output signal 36 a (Wa) as resultof a majority of two-out-of-three voting among signals from PPM A, SPMA, and ISD 33 a. Output signal 36 is used to disconnect the associatedoutput 63 from output 61 of system 11 in the event of a fault occurrencein output controller 40. The voter component B, as shown in FIG. 6B, isidentical to voter component A, and has a similar connection to PPM B,SPM B, and ISD 33 b due to the symmetrical configuration of the system11. PPM A-B, SPM A-B, and ISD A-B sets signals on the associatedcommunication lines 25 a-c, 27 a-c, and 28 a-c to be deactivated duringnormal operation of the system 11, by holding each signal in a logical‘1’ state. It should also be appreciated, that the TMR diagnosticdescribed above allows the system to operate with one working outputcontroller 40 in the event that the other output controllers 40 of theother channel fail. Such operation of TMR diagnostic that has no singlepoint of failure ensures that fault occurrences in the associated outputcontroller are identified.

Continuing, the logic circuit A (67 a) is in operative communicationwith the voting network 54 a via communication lines 54-1 a, 54-2 a, and54-3 a. The communication lines 54-1 a, 54-2 a, and 54-3 a are coupledwith isolation drivers 57-1 a, 57-2 a and 57-3 a respectively, which arein operative communication with switches 56-1 a, 56-2 a, and 56-3 a thatconnected in series between the associated power supply V2 and output 63a, which, in turn, are coupled with load 66 of the system 11. Outputs 63a-b and associated switches 56 a-b are connected in parallel to eachother and are coupled to the load 66 and the output 61 because ofsymmetrical configuration of the system 11. This configuration allowsthe system 11 to perform two-out-of-two (2-of-2) voting among outputdata A, and B. Furthermore, if two PPM or two SPM are failingconcurrently, the system 11 continues perform 2-of-2 voting since eachchannel still produces two sets of output data that are generated eitherby two PPM-s or by two SPM-s. The system 11, therefore, continues to beoperational in the presence of up two faults occurring in the PPM A-B orin the SPM A-B. An alternative method may be for the PPM A-B and SPM A-Bto use three-out-of-four voting among data A1, A2, and data B1, B2 inchannels A and B respectively instead of using 2-of-2 voting in the OC Aand in OC B.

If the system operates with the use of analog modules, then an analogmodule in each channel utilizes the output controller that is coupledwith a digital-to-analog converter (DAC). The outputs of the DAC in eachchannel are coupled with the conventional current summing circuit (CSC),which provides output 61 of the system 10 as a mid-value among theoutput currents that are produced by the first and second channels ofthe system 11. The current summing circuit is able to keep the samevalue of output current in the event that one channel fails. (Analogoutput modules are not shown in FIG. 5 for the sake of simplicity). TheTriple Redundant (TMR) diagnostic used in the digital and in the analogmodule includes a 2-of-3 voter 31 that is coupled with an impropersequence detector (ISD) 33 and is coupled with an associated PPM and SPMin each channel.

Continuing, current/voltage sensors 59 are shown in FIGS. 6A-B, whichare used in each channel is used to verify a value of electrical currentpassing through the switches 56 a-b. The current/voltage sensor 59 a forexample, may also be able to check a value of the voltage across a load66. In addition, a feedback line 60 a provides a controller 40 a tomonitor the load 66 state and the condition of the switches 56 a.

Next, the logic circuit 67 a of FIG. 6A, which is slightly differentwith the logic circuit shown in FIG. 3A of the system 10 is set forth.Specifically, the logic circuit 67 a has logic elements G1-G12, withoutputs G10, G11, and G12 that are inverted by isolation drivers 57-1 a,57-2 a, and 57-3 a that are respectively coupled with power switches56-1 a, 56-2 a, and 56-3 a located on the voting network 54 a. It shouldbe appreciated that the isolation driver 57 may comprise anoptoelectronic isolation driver, however, the isolation driver 57 maycomprise any suitable device. It should also be appreciated that theswitches 56-1 a, 56-2 a, and 56-3 a may comprise MOSFET powertransistors for example, as shown, or any other controllable switches.

It is next considered the logic circuit 67 a and the voting network 54 aoperation in FIG. 6A. It should be appreciated that the identifier (′)used herein identifies that a value is an inverse value. The output ofgate G8 is given as:

ÂWa+B̂Wb+Â(Wb)′=X2 a, that we defined X2 a for simplicity. Output X2 a iscoupled to inputs G1, G3, and G12. On the input of G1, occurs signals Aand X2 a, while the output of G1 produces signal ÂX2 a.

The output controller A (OC A) sets logical signal Da=‘1’ and sets itsinverse signal (Da)′=‘0’ on the first inputs of G2 and G3 respectivelywhen there is no disparity between PPM A and SPM A data, which aredelivered to the output controller A (OC A). The OC A sets the logicalsignal Da=‘0’ and sets its inverse signal (Da)′=‘1’ on the first inputsof G2 and G3 respectively in the event that a disparity between PPM Aand SPM A data is discovered. Signal X2 a occurs on the second input ofG3, and signal ÂX2 a occurs on the second input of G2. The output of G2then produces signal (ÂX2 âDa)′, while the output of G3 produces signal[X2 â(Da)′]′. During normal operation, signal A and signal X2 a mayeach be in a logical ‘1’ or logical ‘0’ state for each controlled point.The output of G4, is given by logic expression as:

Y2a={[(ÂX2âDa)′]̂[(X2â(Da)′]′}=(ÂX2a)′ if Da=‘1’, (Da)′=‘0’ in normaloperation of the system 11. Signals Wa and Wb are normally in ‘1’ state,consequently

X2a=ÂWa+B̂Wb+Â(Wb)′=A+B since (Wb)′=‘0’.

As such, Y2 a=Â(A+B) for each controlled point under normal operation,if it is assumed that the system 11 is normally energized, then Y2a=‘1’. Y2 a on output G4 is inverted twice: first Y2 a is inverted to‘0’ by gate G11 that provides ‘0’ input for the isolated driver 57-2 a;and second, the output of driver 57-2 a is inverted to ‘1’ on input S-2a, which forces switch 56-2 a to be in ON state.

Signal X2 a is coupled with one input of gate G12, with another input ofwhich being coupled with signal 36 a (Wa). Gate 12 output signal isdefined as Y2 a=(X2 âWa)′=A+B. When system 11 in an energized state,signal X2 a=‘1’ and signal Wa=‘1’. Gate 12 then gives an output signal(X2 âWa)′=‘0’. The isolation driver 57-3 a, in turn, inverts signal ‘0’to provide a ‘1’ signal on output S3-a, which is coupled with thecontrol input of power MOSFET 56-3 a. As a result, MOSFET 56-3 a alsocomes to an ON state. The output of G8 is also inverted twice and ittransformed to signal S-3 a=‘1’ that forces switch 56-3 a to be in an ONstate. In addition, the output controller 40 a during normal operationsets signal Sa=‘1’ that produces signal (SâWa)′=‘0’ on the output ofgate 10. The isolation driver 57-1 a in turn inverts this signal ‘0’ forsetting ‘1’ signal on output S1-a, which is coupled with the controlinput of a fault recovery valve (FRV) 56-1 a, which in turn goes to “ON”state in normal operation of the system 11. It should be appreciated,that the fault recovery gate or valve A may also comprise a MOSFET powerswitch. All power switches 56-1 a, 56-2 a, and 56-3 a, therefore, willbe in an “ON” state allowing the output 63 a to be in a normallyenergized. The output 63 a for each controlled point is defined as alogical product that provides 56-1 a, 56-2 a, and 56-3 switches inaccordance with corresponding signals S-1 a, S-2 a, and S-3 a that inturn are controlled by the outputs 54-1 a, 54-2 a, and 54-3 a of thelogic circuit 67 a. Output 63 a is equal to: [Â(A+B)]̂(B+A)=Â(A+B). FRVsA-B are used to disconnect the output 63 a-c from the system output 61in the event of fault occurrence in channels A-B.

If a majority of sections of the DRS issue data that indicate that thecontrolled process is going out of a safe range, the controlled processmay be in a dangerous condition. In that event, the PPM A 20 and SPM 22in each channel usually produce output data A=B=‘0’ for each affectedpoint in the controlled process. The logic circuits 67 a, for example,receives signal A=‘0’ and receives signal X2 a=‘0’ from the PPM A 20 avia the corresponding output controller 40 a. Logic circuit 67 a thengives signal Y2 a=‘0’ at the input of gate G11 that inverts signal Y2 ato ‘1’ at output 54-2 a. The isolated driver 57-2 a, in turn, invertssignal ‘1’ to ‘0’ on output S2-a, which drives power MOSFET switch 56-2a to an “OFF” state. Gate 12 then gives output signal (X2 âWa)′=‘1’,since signal X2 a=‘0’. The isolation driver 57-3 a in turn inverts inputsignal ‘0’ to provide ‘1’ signal on output S3-a, which is coupled withthe control input of the power MOSFET 56-3 a. As a result, MOSFET 56-3 agoes to an “OFF” state. Similarly, MOSFET switches 56-2 b and 56-3 b aredriven to an “OFF” state. When power switches 56-1 a, 56-2 a, and 56-3 aare in an “OFF” state, then switches 56-1 b, 56-2 b, and 56-3 b andswitches 56-1 c, 56-2 c, and 56-3 c will also be in an “OFF” state aswell, and the controlled process will be de-energized. The system 11 maybring the process to a safe condition if the majority of data A and Bfor a given controlled point is in a ‘0’ state.

It should be appreciated that all elements and their connectionsdescribed above with the respect of the output controller A, the logiccircuit A, and the voting network A are similar, and are applicable foruse in the components of channel B (FIG. 3B) due to the symmetricalconfiguration of the system 11. As such, the following expressions foroutputs 63 a and 63 b are provided:

Output 63 a=Â(A+B);

Output 63 b=B̂(B+A).

System 11 output 61 is given as the logical sum of outputs 63 a and 63 bsince they are coupled in parallel:

Output 61=Â(A+B)+B̂(B+A)=A+B.  (3)

Thus, the system 11 performs two-out-of-two (2-of-2) majority votingamong data A and data B in normal operation.

The following discussion considers the occurrence of possible permanentfailures in the PPMs A-B or in the SPMs A-B in various channels A-B. Inparticular, each output controller has a windowed timer that verifies ifthe associated PPM and SPM delivered output data over buses 12 and 14 ontime. If, for example, the PPM A or SPM A fails to deliver the outputdata on time, the output controller 40 a indicates a failure occurrencein PPM A/SPM A or in both of them. In the event that up to two PPMs orup to two SPMs concurrently fail, the system 11 continues to beoperational with a healthy PPM 20 or with a healthy SPM 22 in eachchannel A-B. The system 11, therefore, still performs 2-of-2 voting eventhrough up to two PPMs 20 or up to two SPMs 22 fail concurrently, sinceeach channel provides output data that is produced by the PPM or by theSPM. The system 11, therefore, provides a high level of fault tolerancewith respect to permanent faults that occur in the PPM or SPM.

It is now considered that outputs 63 a, 63 b, and 63 c, and taking A andB data and all signals that: Wa, Wb; Da, (Db)′; and Sa, Sb. Output 63 afor each controlled point is defined as a logical product that provides56-1 a, 56-2 a, and 56-3 switches in accordance with correspondingsignals S-1 a, S-2 a, and S-3 a that, in turn, are controlled by theoutputs 54-1 a, 54-2 a, and 54-3 a of the logic circuit 67 a. Thefollowing logical expression for output 63 a and 63 b includes allsignals in account is transformed to:

$\begin{matrix}{{{{Output}\mspace{14mu} 63\; a} = {{\left( {S\text{-}1\; a} \right)\left( {S\text{-}2\; a} \right)} = {{{SaAWa}\left\lbrack {{Awa} + {BWb} + {A({Wb})}^{\prime}} \right\rbrack}{{Da}++}{{SaWa}\left\lbrack {{AWa} + {BWb} + {A({Wb})}^{\prime}} \right\rbrack}({Da})^{\prime}}}}{{{Output}\mspace{14mu} 63\; b} = {{\left( {S\text{-}1\; b} \right)\left( {S\text{-}2\; b} \right)} = {{{SbBWb}\left\lbrack {{BWb} + {Awa} + {B({Wa})}^{\prime}} \right\rbrack}{{Db}++}{{SaWa}\left\lbrack {{BWb} + {AWa} + {B({Wa})}^{\prime}} \right\rbrack}({Db})^{\prime}}}}} & (3)\end{matrix}$

Outputs 63 a and 63 b are connected in parallel and they are coupled tooutput 61 of the system 11. Output 61 on load 66 is given then as alogical sum:

$\begin{matrix}{{{Output}\mspace{14mu} 61} = {{{{Output}\mspace{14mu} {A\left( {63\; a} \right)}} + {{Output}\mspace{14mu} {B\left( {63\; b} \right)}}}=={{{{SaAWa}\left\lbrack {{Awa} + {BWb} + {A({Wb})}^{\prime}} \right\rbrack}{Da}} + {{{SaWa}\left\lbrack {{AWa} + {BWb} + {A\left( {Wb}^{\prime} \right)}} \right\rbrack}{({Da})^{\prime}++}{{SbBWb}\left\lbrack {{BWb} + {Awa} + {B({Wa})}^{\prime}} \right\rbrack}{Db}} + {{{SbWb}\left\lbrack {{BWb} + {AWa} + {B({Wa})}^{\prime}} \right\rbrack}({Db})^{\prime}}}}} & (4)\end{matrix}$

As such, in expression (4) channel A produces the data Â(A+B), channel Bproduces the data B̂(B+A), and system 11 gives the output 61 that isequal to:

Output 61=Â(A+B)+B̂(B+A)=A+B, since Wa=Wb=Sa=Sb=‘1’ in normal system 11operation.

Da=‘1’, (Da)′=0 if no disparity is found in data A and B; Da=‘0’,(Da)′=‘1’ when disparity in data A and B exists. The system 11 therebyprovides an enhanced 2-out-of-2D shutdown logic operation.

Next, the operation of the system 11 is considered when a disparity ofthe output data exists within the output controller 40 a. In the eventthat the output controller 40 a receives output data from the PPM A andthe SPM A where a disparity exists, the output controller 40 a countsthis data as undefined, and sets a logical “Low” state for the outputdata A on the inputs of the logic circuit 67 a for each point that hasreceived different data. The output controller 40 a also sets the signalDa to a ‘0’ state and signal (Da)′ to a ‘1’ state for these points. Thelogical expression (4) is then given as: Output 61=Output A (63a)+Output B (63 b)=B+B=B, since Da=‘0’, (Da)′=‘1’.

The output controller A uses output data B that it has received from thecontroller B, however the system 11 continues to operate by using outputdata B in both controllers A and B. Similarly, the system 11 providesoutput 61=A+A=A, in the event that a disparity is discovered in theoutput controller B due to the symmetrical configuration of the system11.

In the event that output controller A fails due to a permanent (hard)failure, the associated PPM A, SPM A and ISD 33 a recognize suchcondition, and issue signals 25 a and 27 a providing an alarm signalWa=‘0’ on output 36 a of the voter component 31 a, which, in turn,disconnects output 63 a from system 11 output 61 and load 66. Similarly,if the output controller B fails permanently the associated PPM B, SPM Band ISD 33 b recognize such condition, and issue signals 25 b and 27 bproviding an alarm signal Wb=‘0’ on output 36 a of the voter component31 a, which, in turn, disconnects output 63 b from system 11 output 61and load 66.

The signal Wa=‘0’ is coupled to the inputs of the gates G10, G11, andG12 that forces switches 56 a to be in an OFF state, therebydisconnecting output 63 a from system 11 output 61 and load 66. Output61 is given then as: output 61=B. Output 61=A in the event that outputcontroller B fails. Accordingly, the faulty output controller B may beonline replaced, with a new healthy one.

In the event that the PPM or SPM fails and the output controllerconcurrently fails in the same channel, the healthy PPM or healthy SPMstill check the condition of the output controller, as the ISD 33 does.If, for example, PPM A and output controller 40 a concurrently fail, thevoter component 31 a continues to provide an alarm signal Wa (36) as themajority voting of two signals issued by healthy SPM A and ISD 33 a.Alarm signal Wa occurs on the corresponding input of logic circuit 67 a,that in response, disconnects output 63 a from the output 61. The system11, however, continues to operate with healthy channel B in the presenceof two failures in channel A. If the PPM B and output controller Bconcurrently fail, the system 11 continues to operate with healthychannel A in the presence of two failures due to the symmetricalconfiguration of the system 11. Similar operation occurs in the eventthat any SPM and the associated output controller fail due to thesymmetrical configuration of the system 11. In the event that the outputcontroller 40 and the associated ISD 33 concurrently fail in the samechannel in a way that ISD 33 cannot discover a fault in the outputcontroller 40, then two PPM and SPM in this channel issues ‘0’ signal onlines 25 and 27 as inputs of the voter component 31 respectively. Thesesignals force the voter component 31 to issue an alarm signal 36=‘0’,which disconnects the faulty output 63 from the system output 61.

The system 11 therefore continues to remain operational in the presenceof any single point of failure, either permanent or transient, and maytolerate some kind of two faults. The system performs a shutdown processthat passes the process into a safety condition if all channels A-Bconcurrently fail.

The system 11 utilizes two identical power supplies for providing powerto channels A and B. Such configuration of the power supplies allows thesystem 11 to remain operational if at least one power supply out of twois healthy. In addition, each power supply includes the necessarycomponents for detecting a fault occurrence in a given power supply andfor preventing fault penetration to the power supply associated with theother channel.

In addition, the system 11 uses diverse redundancy as a protectionagainst a common cause failure. In one aspect, the system includes twoPPMs A-B, which are identical to each other with regard to hardware andsoftware. The system 11 includes two SPMs A-B, which are identical toeach other with regard hardware and software. The PPM A-B and SPM A-B,however, are different in hardware and software with respect to eachother, allowing the system 11 to practically eliminate a common causefailure that is the result of software design errors or hardware faults.An alternative approach allows for a decrease the probability of commoncause failures by the use of PPMs A-B and SPMs A-B having the samehardware and software, and to use functional block diagram (FBD)language for developing the application program for the PPM A-B and forSPM A-B. The application program is divided into segments, with eachsegment being executed within one scan period, and the segments beingexecuted in the order that are defined by the user's logic. Thisapproach allows the system to use the same software and hardware for theprimary and secondary processor modules, and significantly decreases theprobability of a common cause failure. In addition, such approach ineach channel enables the system 11 to replace online faulty primary orfaulty secondary processors with a new one. The healthy processor modulethen reprograms new processor module, since both the processor modulesutilize the same software and hardware.

Thus, system 11 provides a reduced cost system as compared to theultra-reliable system 10 described above for the first embodimentwithout significant sacrifice of system tolerance to faults: the system11 has no single point of failure and continues to operate properly uponthe occurrence of some typical two faults. As such, the system 11 can becertified up to SIL 3 in accordance with standards 61508 and 61511.Furthermore, the system 11 employs only two I/O circuits that allow adecreased number of elements in the I/O circuits, which result in thesystem 11 having I/O circuits with a lower cost.

Another embodiment of a redundant computer system is referred to bynumeral 13, as shown in FIG. 7, and is primarily designed to providesafety for a typical distributed control system, but it can also be usedin stand-alone mode. In particular, the system is referred to as atwo-channel computer system (DCS) 13, and includes components that areequivalent to those utilized by the DDS system 11 and the URC system 10,but utilizes a number of components that are significantly less than theelements of the URC system 10. The DCS 13 includes channels A and B,each of which includes identical central processors 88, input modules86, and the output modules that includes output controllers 40, logiccircuits 69, and voting networks 54. FIG. 7 shows only single controlledpoint for the sake of reader's understanding. The input modules 86 a-boperatively communicate with a single sensor 51 to receive processinformation for each controlled point and transform this informationinto a digital format, whereupon the input data is transferred to theassociated central processors CP A-B 88 via interfaces 38 a-b throughI/O buses 80 a-b. The CP A (88 a) and CP B (88 b) are synchronized viabus 100 to receive input data simultaneously from their associated inputmodule 86 a-b.

The CP A and CP B calculate whether the input data is higher than thepredetermined first and second limits or not. The value of a first limit(FL) is usually less than a value of a second limit (SL). The result ofthese calculations presented for each controlled point is in asingle-bit format. If the input data is less than the first limit inboth channels A-B, CP A and CP B use the input data for executing anapplication program and they send output data to the associated outputcontroller 40 and further to the outputs 63, which in turn provides theprocess to be in energized state. In the event that the input data ishigher than the second limit in one channel, it means that the processmay be in dangerous state. The system 13 performs a process shutdown bypassing the process to the safety state if the input data is higher thanthe second limits in all channels of the system.

The difference of the input data received by CP A and CP B for somecontrolled points may be due to sensor faults or due to the occurrenceof transient faults, because of that, the outputs 63 a-b of the systemmay be forced to stop or be suspended until this difference disappearsor is rectified after replacing faulty sensors. During normal operation,output data goes to the associated output module, which provides thesystem output 61 as result of two-out-of-two (2-of-2) voting amongoutput data produced by A-B channels.

The system 13 operates in a cyclical basis, whereby the operation cycleperiod of the system 13 is defined by a scan time, which is primarilycomposed of the time required for input data polling, applicationprogram execution, and the time required for transfer output data to theoutput module. The application program execution and input data pollingare overlapped. The CP A and CP B then uses input data for synchronouslyexecuting an application program and each provide two copies of theoutput data as result of application program execution. The CP A thensends a first copy of the output data to the output controller A (OC A)through bus 80 a and interface 37-1 a, and sends a second copy of outputdata to the output controller B (OC B) through bus 98 a and interface37-2 b. At the same time, the CP B sends first copy of the output datato the OC B through bus 80 b and the interface 37-1 b, and then sends asecond copy of output data to the OC A through the bus 98 b and theinterface 37-2 a. Each output controller 40, therefore, receives outputdata from the CP A and from the CP B through buses 80 a-b and 98 a-b, asit is shown in FIGS. 7, 8A and 8B. Each output controller 40, duringcommunication with the associated CP A and CP B, verifies theircondition by a windowed timer that is embedded in the output controller40 for choosing the correct output data that is produced by CP A and CPB. The output controller 40 a compares the output data that it receivesfrom the associated CP A and CP B. The output controller 40 a by defaultuses the output data that is received from CP A if the output data of CPA and CP B do not have a disparity. In the event that CP A fails, theoutput controller 40 b uses the output data that is produced by theassociated CP B. If the output controllers 40 A-B discover a disparitybetween the output data that is produced by the CPA and CPB for somecontrolled points, it may be due to the occurrence of transient faultsin CP A or in CP B. The output data with disparity is counted asdoubtful, and this data will not be used for controlled points withdisparity. Because of that, the output controller 40 activates disparitysignal D indicating that the system 10 is not utilizing this doubtfuldata. The output controller 40 activates disparity signal D on the inputof the logic circuit 69, thereby preventing the system 13 from usingthis doubtful data. The output controller (OC) 40 then sends zero outputdata to the neighboring output controller and receives therefrom outputdata through bus 55 to substitute the doubtful output data.

The output data that the output controller receives from the CP A and CPB is defined herein as A and B. The output controller then calculatessignal D for each controlled point in channel A using the followingequation:

D={XNOR with A, B},

where Da is equal to ‘1’, if there is no disparity between data A anddata B. If a disparity exists between data A and data B, then outputcontroller 40 sets inverse signal (Da)′ equal to “0”. A truth table isshown in Table 5 below.

TABLE 5 A B XNOR Da Da′ 0 0 1 1 0 1 1 1 1 0 1 0 0 0 1 0 1 0 0 1

In addition, the output controller uses any suitable technique, such asSEC-DED, to correct any one fault and to indicate a two fault occurrencein CP A and CP B during their communication with the output controller40 through the associated buses 80 a-b and 98 a-b. The comparisondiagnostic that is described above is able to restore the system 13 toproper operation after the occurrence of single permanent or transientpoint of failure in each channel. When a disparity between the outputdata occurs in output controllers 40 a and 40 b concurrently, eachoutput controller repeats the process of receiving output data up tothree times, until the transient fault disappears. If the disparitypersists for a longer period than that defined by the safety processtime, the system 13 performs a process shutdown by passing the processto the safety state.

FIGS. 8A-B show the components that each output module a-b includes, asfollows: output controller 40 a-b, voting component 31 a-b, and animproper sequence detector (ISD) 33 a-b.

In addition, the CPs 88 a-b are in operative communication with a votercomponent 31 a by a line 25 a and 27 a, and communicate with a votercomponent 31 b by a line 25 b and 27 b as shown in FIGS. 7 and 8A-B.Improper sequence detectors (ISD) 33 a and 33 b are used forcontinuously monitoring both time-based and logical correctness of theprograms that the output modules 40 a and 40 b execute. The ISD 33 aactivates an output signal on the input of the voter component 31 a inthe event that the output module 40 a fails. The CP A verifies theconditions of the OC A and OC B during communication with them over thebuses 80 a and 98 a respectively. Similarly, the CP B verifies theconditions of OC B and OC A during communication with them over buses 80b and 98 b respectively. In addition, the CP A connects to a first andsecond input of the voter components 31 a and 31 b by lines 25 a and 27b respectively. Similarly, the CP B connects to a first and second ofthe inputs of the voter components 31 b and 31 a by lines 25 b and 27 arespectively. In addition, the outputs of ISD-s 33 a and 33 b areconnected to a third input of the voter components 31 a and 31 brespectively.

The voter component 31 a includes a plurality of parallel voting groups39-1 a, 39-2 a, and 39-3 a, as shown in FIG. 8A, that are coupledbetween a voltage source A and a resistor 29 a, which is connected to aground node. Each voting group 39 a includes power switches, such as alow power MOSFET or any other suitable transistor or relay for example,connected in series. A first switch of group 39-1 a and a second switchof group 39-2 a are coupled to line 25 a, that are controlled by CP A. Afirst switch of group 39-3 a and a second switch of group 39-1 a arecoupled to line 27 a, which are controlled by CP B. A first switch ofgroup 39-2 a and a second switch of group 39-3 a are coupled to line 28a, which are controlled by ISD 33 a. Both CP A and CP B monitor theconditions of the output controllers 40 a and 40 b during communicationwith them through buses 80 a-b and 98 a-b. CP A, CP B, and ISD 33 a-bsets respective signals to a state on lines 25 a-b, 27 a-b, and 28 a-bduring normal system 13 operation, which provides that the outputs 36 aand 36 b of voter components 31 a and 31 b be normally in a state. Suchconfiguration of the 2-of-3 voter with SP A, SP B, and ISD in eachchannel has no single point of failure. During normal system 13operation, therefore, the voter component 31 a produces output signal 36a as result of a majority of two-out-of-three voting among signals,which the CP A, CP B, and the ISD 33 a produce on the inputs of thevoter component 31 a. If, for example, the output controller 40 a fails,the CP A activates a ‘0’ signal on line 25 a, while the CP B activates a‘0’ signal on line 27 a. As a result, at least two signals in a ‘0’state occur simultaneously on two inputs of the voter component 31 a,which are sufficient to provide a majority of signals in a ‘0’ state forallowing them to have a ‘0’ signal in the output 36 a (Wa) of the votercomponent 31 a. Signal Wa in a ‘0’ state goes to corresponding input ofthe logic circuit 67 a, which in turn disconnects output 63 a fromoutput 61 of the system 13. The voter component B is identical to votercomponent A and has similar connection with CP B, CP A, and ISD 33 b dueto the symmetrical configuration of the system 13. Consequently, if theoutput controller 40 b fails, the CP B activates the ‘0’ signal on line25 b, while the CP A activates the ‘0’ signal on line 27 b. As a result,at least two signals in the ‘0’ state occur simultaneously in two inputsof the voter component 31 b, which are sufficient to provide a majorityof signals in a ‘0’ state to have a ‘0’ signal on the output 36 b (Wb)of the voter component 31 b. Signal Wb in a ‘0’ state goes to acorresponding input of the logic circuit B, which in turn disconnectsthe output 63 b from the output 61 of the system 13. The diagnosticsconsidered above allows the system 13 to be effective in discoveringpossible failures in the output controllers 40 a-b, since the 2-of-3voter component 31 a-b configuration has no single point of failure. Inaddition, the output controller A is able to operatively communicatewith the output controller B and the output controller C via thecommunication bus 55. In some embodiments, the communication buscomprises a read-only bus. As such, the communication bus 55 enableseach output controller 40 a-b to communicate with one of the otheroutput controllers, such as by sending and/or receiving output data.Continuing, the output controller A (OC A) sends output data A to theoutput controller B through bus 55-2, and receives output data B fromthe output controller B at the same time through bus 55-1. The outputcontroller 40 a issues single-bit data A and B, and issues signals Sa,Da, and inverted signal (Da)′ on the corresponding inputs of the logiccircuit 67 a. Similarly, the output controller 40 b issues data A anddata B, and issues signals Sb, Db, and inverted signal (Db)′ on thecorresponding inputs of logic circuit 67 b.

FIGS. 8A-B show the current/voltage sensors 59 in each channel, whichare utilized to verify a value of electrical current passing through theswitches 56 a-c. In addition, sensor 59 a is able to check a value ofthe voltage of a load 66. Furthermore, a feedback line 60 a provides acontroller 40 a to monitor the load 66 state and the condition of theswitch 56 a. The logic circuit 67 a-b is now considered, which issimilar to the logic circuit 53 a-b that is shown in FIGS. 6A-B. Data Aand data B in FIGS. 8A-B are named A and B for the sake of simplicity.First, we consider signals on the outputs of gates G1-G4 and G8, asshown in FIG. 8A. On the G1 output is ÂX3 a, where X3 a is provided asthe output of gate G8. Output X3 a is equal to a logical sum of thethree inputs of gate G8. The first input of G8 is the output of gate G6that is equal Â(Wb)′, while the second and third inputs of G8 are equalto B̂Wb and ÂWa respectively. Identifier (′) indicates that a value is aninverse value in the discussion presented herein. The output of gate G8is given as:

Â(Wb)′+B̂Wb+ÂWa=X3 a, which is defined herein as X3 a for clarity. Itshould be appreciated that both inputs of G6 are coupled for the system13 only. Output G8, which is equal to X3 a is coupled to inputs G1, G3,and G12. On inputs of G1 occur signals A and X3 a, and the output of G1produces signal ÂX3 a. The output controller A (OC A) sets a logicalsignal Da=‘1’ and sets its inverse signal (Da)′=‘0’ on the first inputsof G2 and G3 respectively when there is no disparity between CPA and CPBdata in OC A. The output controller A (OC A) sets the logical signalDa=‘0’ and sets its inverse signal (Da)′=‘1’ on first inputs of G2 andG3 respectively in the event that a disparity between data A and B isdiscovered. Signal X3 a occurs on a second input of G3 and signal ÂX3 aoccurs on a second input of G1. The output of G2 then produces signal(ÂX3 âDa)′, while the output of G3 produces signal X3 â(Da)′. As aresult, G4 produces a signal [(ÂX3 âDa)]̂[X3 â(Da)′]′=Y3 a, which isidentified herein as Y3 a for simplicity. Gate 4 output is given bylogic expression as: Y3 a={[(ÂX3 a ̂(Da)′]̂[(X3 â(Da)′]′}′.Similar results were achieved for X3 b and Y3 b for channel B by usingFIG. 8B: X3 b=B̂(Wa)′+ÂWa+B̂Wb. Y3 b={[(B̂X3 b̂Db)′]̂[(X3 b̂(Db)′]′}′.

During normal operation, signal A and signal X3 a may each be a logical‘1’ or a logical ‘0’ for each controlled point. Signal Da=‘1’ and signal(Da)′=‘0’ in normal operation when output data A and B produced by CPAand CPB are equal. During normal operation, signals Wa=Wb=Wc=‘1’. If thesystem 13 is normally energized, then A=X3 a=X3 b=‘1’ since A=B=1. Andthe logical signal Y3 a for each controlled point given as: Y3a={[(1̂1)′]′̂[(1̂0]′]}′=[0̂(1̂0)]′=(0̂0)′=‘1’. Signals Y3 a and Wa are coupledto gate G11 that provides the output signal 54-2 a on input of theisolation driver 57-2 a as an inverse signal (Y3 âWa)′=(1̂1)′=‘0’. Theisolation driver 57-2 a is used to provide isolation to a logic sectionof the system 10 from its power section. It should be appreciated thatthe isolation driver 57-2 a may comprise an optoelectronic isolationdriver; however, isolation driver 57-2 a may comprise any suitabledevice. The isolation driver 57-2 a, in turn, inverts signal ‘0’ toprovide a ‘1’ signal on output S2-a, which is coupled with the controlinput of power MOSFET 56-2 a, and as a result, MOSFET 56-2 a comes to an“ON” state.

Signal X3 a is coupled with one input of gate G12, while another inputof which is coupled with signal Wa. When system 10 is in an energizedstate, signal X3 a=‘1’ and signal Wa=‘1’. Gate 12 then gives outputsignal (X3 âWa)′=‘0’. The isolation driver 57-3 a, in turn, invertssignal ‘0’ to provide a ‘1’ signal on output S3-a, which is coupled witha control input of the power MOSFET 56-3 a. As a result, MOSFET 56-3 agoes to an “ON” state. The output controller 40 a in normal operationsets signal Sa=‘1’ at one input of gate 10, another input of which iscoupled with signal Wa. The isolation driver 57-1 a, in turn, invertssignal ‘0’ to provide a ‘1’ signal on the output S1-a, which is coupledwith the control input of a fault recovery valve 56-1 a that goes to an“ON” state. It should be appreciated that the fault recovery gate mayalso comprise a MOSFET power switch. All of the power switches 56-1 a,56-2 a, and 56-3 a, therefore, will be in an “ON” state provided thatoutput 63 a is energized. FIGS. 8A-B show the current/voltage sensors 59in each channel, which are utilized to verify a value of electricalcurrent passing through the switches 56 a-c. In addition, sensor 59 a isable to check a value of the voltage of a load 66. Furthermore, afeedback line 60 a provides a controller 40 a to monitor the load 66state and the condition of the Fault Recovery Switch (FRS) 56 a.

In general, the output controller 40 b, the logic circuit 67 b, and thevoting network 54 b operate similarly as the corresponding elements inFIG. 8A, as described above, because the elements a and b in FIGS. 8A-Bare structurally equivalent. It should be appreciated, that allconnections described above with the respect of the output controller A,logic circuit A, and voting network A are similar and applicable forcontrollers B (FIG. 8B) due to the symmetrical configuration of thesystem 13. In the event that the output data that is produced by the CPA and the CP B have a disparity, it would be due to the occurrence ofundetected transient faults in the CP A or in the CP B, if a hardfailure in the CP A and in the CP B has not been identified.

Outputs 63 a, and 63 b are now presented, whereby output 63 a for eachcontrolled point is defined as a logical product that switches 56-1 a,56-2 a, and 56-3 provide in accordance with corresponding signals S-1 a,S-2 a, and S-3 a that, in turn, are controlled by the outputs 54-1 a,54-2 a, and 54-3 a. The output controller 40 a sets Da signal=‘1’ and(Da)′ signal=‘0’ in this event. Outputs 63 a, and 63 b are connected inparallel and they are coupled to output 61 of the system 13. Thefollowing logical expression for outputs 63 a and 63 b includes allsignals, and given as a logical sum:

Output 61=Output A (63a)+Output B(63b)=SâÂWâ[ÂWa+B̂Wb+Â(Wb)′]̂Da+SâWâ[ÂWa+B̂Wb+Â(Wb)′]̂(Da)′+Sb̂B̂Wb̂[B̂Wb+ÂWa+B̂(Wa)′]̂Db+Sb̂Wb̂[B̂Wb+ÂWa+B̂(Wa)′]̂(Db)′  (5)

It should be appreciated that a first product contains data A-B, whiledata A-B is in absence in the first product of a second term.

During normal operation, the Wa=Wb=‘1’; Sa=Sb=‘1’; Da=‘1’, (Da)′=‘0’. Assuch, in expression (5) CPA and CP B produce data Â(A+B) and producedata B̂(B+A) respectively, and the system 13 provides the output 61 to beequal:

Output 61=Â(A+B)+B̂(B+A)=A+B.  (6)

Thus, the system 13 performs two-out-of-two (2-of-2) majority votingamong data A and B under fault-free circumstances as it follows from thelogical expression (6).

Next, the operation of the system 13 is considered when a disparity ofthe output data exists within the output controller 40 a. In the eventthat the output controller 40 a receives output data from the CP A andthe CP B, where a disparity exists between their data for some points,the output controller 40 a counts this data as undefined and sets alogical “Low” state for the output data A on the inputs of the logiccircuit 67 a for each point that has received different data. The outputcontroller 40 a also sets disparity signal Da to a ‘0’ state and signal(Da)′ to a ‘1’ state for these points. The logical expression (6) isthen given as:

Output 61=Output A (63a)+Output B (63b)=B+B=B, since Da=‘0’, (Da)′=‘1’.

The output controller A uses output data B that it receives from thecontroller B over bus 55. The system 13, therefore, continues to operateby using output data B in both controllers A and B. The system 13, dueto its symmetrical configuration, provides output 61=A+A=A in the eventthat a disparity is discovered in the output controller B.

In the event that output controller A fails due to a permanent (hard)failure, the CP A and CP B recognize this fault during communicationwith controller A and sets alarm signals to a ‘0’ state on lines 25 aand 27 a respectively. At least two signals in a ‘0’ state aresufficient to have the voter component 31 a provide a ‘0’ state onoutput Wa (36 a), even though ISD 33 a fails to discover a faultoccurrence in output controller A. As shown in FIG. 8A, the signalWa=‘0’ is coupled to the inputs of the gates G10, G11, and G12, whichforces switches 56 a to be in an OFF state, thereby disconnecting output63 a from system 13 output 61 and load 66. Output 61 is then equal to B.The signal Wa is also coupled with a second input of gate 9 to provideA(Wa) output of this gate. Similarly, if the output controller B failsdue to a permanent (hard) failure, the CP B and CP A recognize thisfault during communication with controller B and set alarm signals to a‘0’ state on lines 25 b and 27 b respectively. As shown in FIG. 8B, thesignal Wb=‘0’ is coupled to inputs of the gates G10, G11, and G12 thatforces switches 56 b to be in an OFF state, thereby disconnecting output63 b from system 13 output 61 and the load 66. Output 61 is then equalto A as it follows from the equation 5. In the event that the CP A failsbecause of the occurrence of a hard failure, CP B still provides outputdata to both output controllers B and A through bus 80 b and 98 brespectively. If the CP B fails, the CP A still provides output data toboth output controllers A and B through bus 80 a and 98 a. In the eventthat CP A and output controller A concurrently fail, the system 13continues to remain operational with the healthy CP B and the healthyoutput controller B. The system 13 also remains operational if the CP Aand output controller B located in different channels fail concurrently,because the healthy CP B will operate with the healthy output controllerA through bus 98 b. If the CP B and the output controller A failconcurrently, the system 13 again continues to remain operational withthe healthy CP A and the healthy output controller B. The system 13therefore provides tolerance to any single point of failure, eitherpermanent or transient, and continues to operate in the presence of somekind of two faults. In the event that two output controllers A and Bfail or CP A and CP B concurrently fail, the system 13 performs ashutdown process by de-energizing the system output 61 and passing thecontrolled process to a safe state.

Continuing, another exemplary operating scenario includes the possibleoccurrence of faults in the logic circuits 67 a-b and in the votingnetwork 54 a-b. Outputs 36 a and 36 b of the voting modules 31 a and 31b serve as inputs for both the logic circuit A and logic circuit B. Inthe event that one logic circuit fails in a way that the associatedelectronic switches are permanently in an ‘OFF’ state, the outputs 63 ofthe associated channels are de-energized, but the system 13 continues tooperate using the other remaining healthy channel. If two electronicswitches in the associated channel fail in a permanently ‘ON’ state forthe same controlled points and the voltage/sensors 56 recognize suchfaults and give this information on line 60 to the associated outputcontroller. The output controller A, for example, activates a signalSa=‘0’ on lines 54-1 a of the logic circuit 67 a. The output of each G10is coupled to the input of the associated isolation driver 57-1 a, whichcontrols a fault recovery valve (FRV) 56-1 a. The output of the G10 goesto ‘1’, output of the isolation driver 57-1 a goes to ‘0’ state forcingthe FRV 56-1 a to be in an ‘OFF’ state, and outputs 63 a arede-energized. The output controller B operates similarly to outputcontroller A as discussed above. In addition, the output controller usesany suitable technique, such as SEC-DED, to correct any one transientfault and to indicate a two fault occurrence in CP A and CP B duringtheir communication with the output controller 40 through the associatedbuses 80 a-b and 98 a-b.

The system 13 therefore continues to remain operational in the presenceof any single point of failure and may tolerate some kind of two faults.In the event that two logic circuits or two output voting networks 54fail in the ‘OFF’ state for the same controlled points, the system 13performs a shutdown process that passes the controlled process in asafety condition.

It should be appreciated that the system 13 utilizes two identical powersupplies for providing power to channels A and B. Each power supplyincludes the necessary hardware and/or software for detecting theoccurrence of a fault in the power supply itself, and for preventingfault penetration into the power supply of the other channel, therebyallowing the system 13 to remain operational if at least one of the twopower supplies remains healthy and operational.

Thus, the system 13 is configured to have reduced cost given its design,by utilizing only two central processors CP A and CP B and two I/O(input/output) circuits that utilize a reduced number of elements. Inaddition, the system is capable of performing fault diagnostics that hasno single point of failure, allowing the system 13 to operate properlyin the presence of some kind of two faults. The architecture of thesystem 13, therefore, is capable of achieving certification of up to SIL3 in accordance with standards 61508 and 61511.

Another embodiment of the various embodiments is a computer system 14that integrates, but maintains as separate, a safety and controlfunctionality (ISC). The safety section 14 a and control section 14 beach includes multiple remote chassis to provide safe control of up tofour or more processes at the same time.

Next, the safety section of the ISC system is presented. Specifically,the safety section 14 a (FIGS. 9, 9A, 9B) includes a main chassis 100that houses two redundant central processors 66 a (CP A) and 66 b (CP B)operating in parallel. The CP A and the CP B each have a communicationmodule, which are separately connected to bus 69 for communicatingbetween the CP A and the CP B, and connected to bus 71 for isolatedcommunication between the safety and control sections of the integratedsystem. The third bus, not shown in FIG. 9, is used for communicationwith external devices, such as a host device and an operator Interface.Each central processor further includes at least one embedded ETHERNETport that operatively communicates with an ETHERNET switch 67 over bus48. An input/output controller 70 (IOC) in each remote chassis that canbe 1-4 in some embodiments, operatively communicates with acorresponding output of the associated ETHERNET switch 67. Each centralprocessor 66 uses an embedded ETHERNET port and an external ETHERNETswitch 67 for scanning input/output controllers 70 over the longdistance bus 73, which can be a fiber optic or copper cable for example.Each remote chassis further includes at least two input module 86 thatreceive information about the controlled process from the single sensor51 for each controlled point. Input modules 86 a-b convert the inputdata so as to be in a digital format, and sends the input data to theassociated IOC 70 through buses 80 a and 80 b. The IOC 70 a and IOC 70 bthen utilize the associated long distance buses 73 and ETHERNET switches67 a, 67 b to transfer the input data to the CP A and to CP Brespectively. The CP A and the CP B execute the application program andthey transfer output data, as a result of the application programexecuting back to the associated IOC 70 a-b over a long distance bus 73,which, in turn, send output data to the associated output controller(OC) 40 a-b over bus 80 a-b. The OC 40 a-b produce outputs oncorresponding inputs of a logic circuit 69 a-b, which coupled with avoting switches 56 to perform 2-of-2 voting between output data thatsaid first and second IOC 70 receive from CP A and CP B.

In addition, the CP A and CP B calculate whether input data is higherthan predetermined limits or not. The result of these calculations ispresented for each controlled point in a single-bit format. The value ofa first limit (FL) is usually less than a value of a second limit (SL).If the input data is less than the first limit in both channels A-B,then the controlled process is in energized state. If the input data ishigher than the second limit in one channel of the system it means thatthe process can be in a dangerous state. The system 13 performs aprocess shutdown by passing the process to the safety state if the inputdata is higher than the second limits in two channels of the system.

Additional components that each remote chassis includes will now bepresented. Each output module includes a diagnostic circuit, thatincludes a voter component 31, an improper sequence detector 33 (ISD),an output controller 40 (OC), a logic circuit (LC) 69, and a votingcircuit 54. The voter component 31 shown in FIGS. 9A and 9B is inoperative communication with each of the logic circuits 69 a and 69 bvia line 36 a (Wa). Logic circuits 69 a-b is in operative communicationwith output controller 40 a-b. The system further includes a TMR typediagnostic in each channel. The TMR diagnostic includes the 2-of-3 voter31, one input of which is coupled with ISD 33 output 28. The votercomponent 31 a, which may be a 2-of-3 voter component includes aplurality of parallel voting groups 39-1 a, 39-2 a, and 39-3 a, whichare coupled between a voltage source A and a resistor 29 a, which isconnected to the ground node. Each group 39 a includes two electronicswitches, such as transistors, connected in series. A first switch ofgroup 39-1 a and a second switch of group 39-2 a are coupled to line 25a, which are controlled by the IOC 70 a. A first switch of group 39-3 aand a second switch of group 39-1 a are coupled to line 27 a, that arecontrolled by the IOC B. A first switch of group 39-2 a and a secondswitch of group 39-3 a are coupled to line 28 a, that are controlled byISD 33 a. The voter component 31 a, therefore, receives three inputsignals from IOC 70 a, IOC 70 b, and from ISD 33 a, and produces outputsignal 36 a (Wa), as result of a majority of two-out-of-three votingamong signals from IOC 70 a, IOC 70 b, and ISD 33 a.

The IOC 70 a and the IOC 70 b periodically monitor conditions of theassociated OC 40 during communication xxx through buses 80 a and 80 b.The ISD 33 a continuously monitors the associated OC 40 a for verifyingboth time-based and logical program execution that the OC 40 performs.The IOC A and the IOC B in normal operation keeps ‘1’ signals on lines25 a and 27 b, as well on lines 25 b and 27 a, respectively. The 2-of-3voter component 31 a produces, in this case, an output signal 36 a=‘1’as the result of a majority voting among signals issued by the IOC 70 a,IOC 70 b, and the ISD 33 a. For example, if OC 40 a fails, the IOC 70 aand ISD 33 a discover this fault and the IOC 70 a sets signal ‘0’ online 25 a, while the ISD 33 a sets signal ‘0’ on the output 28 a, whichis coupled with another input of voter component 31 a. The IOC 70 a,using bus 83, sends a message to the IOC 70 b to set ‘0’ on line 27 afor providing the majority voting for ‘0’ signals on the inputs of thevoter component 31 a even though the ISD 33 a has not discovered a faultoccurrence in the OC 40. The voter component 31 a, in response, producesthe ‘0’ output signal on inputs LC 69 a and LC 69 b. The LC 69 a, inturn, sets the associated electronic switches 56-2 a and 56-3 a in anOFF state for de-energizing the output 63 a from output 61 in the eventthat the OC 40 a fails. When this occurs, the system continues tooperate with a single controller OC 40 b until the replacement of thefaulty output module with a healthy one. Similarly, LC 69 b setselectronic switches 56-2 b and 56-3 b in an OFF state for de-energizingthe output 63 b of the safety section output 61 when the OC 40 b fails.This TMR diagnostic, thereby, allows the safety section to operateproperly with one working OC 40 a, in the event that OC 40 b fails andvice versa. The IOC 70 a then restores a ‘1’ on line 25 a and sends amessage to the IOC 70 b to restore a ‘1’ on line 27 a. Similar systemoperation takes place in the event that the OC 40 b fails. This TMRdiagnostic has no single point of failure, because of that it isconsiderably more effective than those diagnostics currently known. Thesafety section of the system 14 further utilizes SEC-DED technology todecrease the probability of transient faults.

The operation of the logic circuits 69 a-b and the voting networks 54a-b operation (FIGS. 9A-B) will now be discussed. It should beappreciated, that the isolation driver 57 in FIGS. 9A, 9B may comprisean optoelectronic isolation driver, however, the isolation driver 57 maycomprise any suitable device. It should also be appreciated, that theswitches 56-1 a, 56-2 a, and 56-3 a may comprise low power MOSFETtransistors, as shown, or any other controllable switches. Symbol (′)identifies that a value is an inverse value.

The logic circuit 69 a-b which is now presented, is similar to the logiccircuit 69 a-b that is shown in FIGS. 8A-B. Data A and data B in FIGS.9A-B are named A and B for the sake of simplicity. First, we considersignals on the outputs of gates G1-G4 and G8, as shown in FIG. 9A. Onthe G1 output is ÂX4 a, where X4 a is provided as the output of gate G8.Output X4 a is equal to a logical sum of the three inputs of gate G8.The first input of G8 is the output of gate G6 that is equal Â(Wb)′,while the second and third inputs of G8 are equal to B̂Wb and ÂWa,respectively. Identifier (′) indicates that a value is an inverse valuein the discussion presented herein. The output data A=B=‘1’ are in theenergized mode, consequently output of gate 11 is also in ‘0’ state. Theisolation driver 57-2 a inverts signal ‘0’ to provide ‘1’ signal onoutput S2-a, which is coupled to control input of power MOSFET 56-2 a.

Output 63 a is defined thereby to be equal to Â(A+B). Output 63 b (FIG.9B) is defined similarly to output 63 a, whereby output 63 b=B̂(B+A) dueto the symmetrical section 14 a configuration. The following logicalexpression, Eq. 7, for outputs 63 a and 63 b includes all signals, isgiven as a logical sum:

Output 61=Output A (63 a)+Output B (63b)=SâÂWâ[ÂWa+B̂Wb+Â(Wb)′]̂Da+SâWâ[ÂWa+B̂Wb+Â(Wb)′]̂(Da)′+Sb̂B̂Wb̂[B̂Wb+ÂWa+B̂(Wa)′]̂Db+Sb̂Wb̂[B̂Wb+ÂWa+B̂(Wa)′]̂(Db)′

The output controller a-b in each scan receiving/sending from/to outputcontroller b-a output data B over read bus 55. As such, in expression(7) IOC A and IOC B received output data A and B from CP A and CP B andproduce output data Â(A+B) and B̂(B+A), on outputs of output controllersA-B respectively, and the safety section of the system 14 provides theoutput 61 to be equal:

Output 61=Â(A+B)+B̂(B+A)=A+B in normal system operation.

The safety section, thereby, performs 2-of-2 voting with the output dataproduced by central processors CP A and CP B. In the event that OC Afails, Wa=‘0’, and the equation (7) is transformed to:

Output 63 a=B̂(B+B)=B, and the safety section performs 1-of-1 voting withthe output data produced by central processor CP B. In the event thatthe OC B fails, Wb=‘0’ and Output 63 b=Â(A+A)=A due to the symmetricalsafety section configuration. Safety section output 61 (SO) is given as:

SO=B, or SO=A.

In addition, the output controller 40 a sets signal Sa=‘1’, and producessignal (SâWa)′=‘0’ on the output of gate 10 in normal operation. Theisolation driver 57-1 a, in turn, inverts this signal ‘0’ for setting‘1’ signal on output S1-a, which is coupled with the control input of afault recovery valve (FRV) 56-1 a, which, in turn, goes to an “ON”state. Power switches 56-1 a, 56-2 a, and 56-3 a is also operation in an“ON” state providing output 63 a to be normally energized. It should beappreciated, that the fault recovery gate 56-1 a may also comprise apower switch such as a MOSFET power switch. The output 63 a for eachcontrolled point is defined as a logical product that MOSFET switches56-1 a, 56-2 a, and 56-3 provides in accordance with correspondingsignals S-1 a, S-2 a, and S-3 a that in turn controlled by the outputs54-1 a, 54-2 a, and 54-3 a of the logic circuit 69 a. In the event thatcontrolled process requires shutdown, the section 14 a obtains dataA=B=‘0’ for de-energizing the process. FRVs A-B are used fordisconnecting the output 63 a-b from the system output 61 in the eventof fault occurrence in logic circuits A-B. For example, if the logiccircuit A fails the output controller 40 a recognizes that sets signalSa=‘0’, and produces signal (SâWa)′=‘1’ on the output of gate 10.

The isolation driver 57-1 a, in turn, inverts this signal ‘1’ forsetting ‘0’ signal on output S1-a, which is coupled with the controlinput of a fault recovery valve (FRV) 56-1 a, which, in turn, goes to an“OFF” state, because of that faulty output 63 a is disconnected fromoutput 61. The safety section in general is able to operate in thepresence of a single fault in any of the safety section components. Thesafety section is also able to operate with one healthy channel if theneighboring channel fails. For example, the safety section performs1-of-1 voting if the CP A and IOC A fail. In the event that the twochannels fail concurrently, the safety section performs a shutdown bypassing the controlled process to a safe state.

The output controller 40 b, the logic circuit 53 b, and the votingnetwork 54 b operate similarly as the corresponding elements describedin FIG. 9A above, as these elements are structurally equivalent toelements a and b in FIGS. 9 A-B. It should be appreciated that allconnections described above with the respect of the output controller A,logic circuit A, and voting network A are similar and are applicable forcontrollers B (FIG. 9B) due to the symmetrical configuration of thesafety section of the system 14. The safety section is able to operatewith one healthy channel if the neighboring channel fails. For example,the safety section performs 1-of-1 voting if the CP A and IOC A fail. Inthe event that the channels fail concurrently, the safety sectionperforms a shutdown by passing the controlled process to a safe state.

For some applications, it is preferable to perform 1-of-2 shutdown logicinstead of 2-of-2 logic. Minor changes in logic 69 allow the safetysection to perform 1-of-2 shutdown logic. In this way, output 61 isgiven as:

Output 61=output 63 a+output 63 b=ÂB+B̂A=ÂB

In the event that physical parameters deviate from the safety range, theCP A and CP B inform the control section that the controlled process isin a dangerous situation. If the safety and control sections cannotovercome the dangerous situation, the safety section brings thecontrolled process into the safety state. The safety section remainoperational in the presence of any single hard/transient fault and mayproperly operate in the presence of some kind of two faults.

The safety section, thereby, further increases the safety level of thecontrol section 14 b in ISC system that is depicted in FIG. 9. Thesafety section and the control section operate completely independently,and have a physically separated protection layers that allow theintegrated system ISC to attain up to SIL 3 requirements of the Standardof IEC 61511.

The control section 14 b of the system 14 includes two identical processcontrollers primary (PC) and secondary (SC) in a back-up redundantconfiguration that is located on a main chassis 108. The PC A (74-1) andthe SC B (74-2) has a communication module, each of which is separatelyconnected to the bus 71 for communicating with the safety section andbetween the PC A and the SC B. Another bus (not shown in FIG. 9) is usedby only the primary controller for communication with external devices,such as a host device and an operator interface. The PC A and the SC Bfurther include at least one embedded ETHERNET port that is operativelyconnected with multiple ETHERNET switches 76 through a bus 72. Thecontrol section further includes multiple remote chassis (1-4), each ofwhich house an input/output controller IOC (79). The PC A and the SC Butilize bus 78 for synchronous scanning IOC 79 in each remote chassis1-4 over a long distance bus 75, which may comprise fiber optic orcopper cable for example. Each IOC 79 operatively communicates with theassociated input modules 1−N that receive input data from control inputs107 and 109. These control inputs can be flow and pressure sensors offinal control elements (that are not shown in FIG. 9 for simplicity), aswell as any other type of sensors. Each IOC 79, through bus 83, receivesinformation about the controlled process from the control inputs 107 and109. IOC 79-1, for example, makes a first copy of the input data for thePC A, and makes a second copy of the input data for the SC B. The PC Aand the SC B use embedded ETHERNET ports for scanning an infinitesequence of the IOC 79 1-4 through buses 75 and the ETHERNET switches76, which are operatively connected to the ETHERNET ports embedded in PCA and in SC B via bus 72. The PC A and SC B receive the first and secondcopy of the input data during scanning, and utilize them for comparisonwith predetermined thresholds, and for synchronously executing anapplication program. Only PC A is selected, however, for sending theresults of the application program execution to the associated IOC 79.

The PC A and SC B operate in a mode, whereby the primary controller (PC)operates in an active mode to provide all communication with the IOC 79,and with the external devices, while the second controller (SC) isplaced in a hot standby mode. The SC automatically enters the activemode in the event that the PC fails. In some embodiments, the systemHC900, produced by the Honeywell Company, may provide an architecturethat the control section partially utilizes although any suitablearchitecture may be used. However, the control section of the ICS may bein some embodiments different from the HC900 architecture with regard tothe following:

(1) hardware and firmware means in the control section define a primaryor secondary status of the PC and CS by default after power up;

(2) Hardware and firmware means in the PC and SC detect their status inany scan by using an embedded serial peripheral interface (SPI) thathouses self-diagnostics;

(3) self-diagnostics also allow the PC and SC to change their statusautomatically from PC to SC, and from SC to PC, if the PC or SC fails.

The manner in which the status of the PC and SC is defined by defaultafter power up will now be presented. We will below use terms PC A andPC B instead of PC A and SC B for positioned in an identicalconfiguration. The PC A and PC B may be located in a side-by-sideposition on a backplane, with each being inserted into an associatedconnector of the backplane. The first connector of the backplane haseight selected pins connected together to a plus terminal of powersupply for obtaining a logical high signal on each of that pins, andproviding thereby an identification word ID=FFh. A second connector ofthe backplane has eight selected pins connected together to a groundterminal of power supply for obtaining a logical low signal on the pinsfor providing identification word ID=00 h. Each process controller 74has an input port that is connected via a connector to associated pinsin the backplane for reading an identification word (ID) correspondingto values presented on the pins. Any process controller 74 that isinserted in the first connector will thereby read its identificationword ID=FFh, while another process controller 74 inserted in the secondconnector will read its identification word ID=00 h. The processcontroller that inserted into the first connector is defined by defaultas the primary controller (PC), while the process controller that isinserted into the second connector is defined by default as thesecondary controller (PC B). The control section 14 b at power up musthave two healthy process controllers, otherwise, a start-up diagnosticor SPI diagnostic will prevent the execution of the system applicationprogram. During normal operation, the statuses of both processcontrollers are constantly indicated. In the event that the primarycontroller fails, the secondary controller automatically obtains theprimary status. In the event that the secondary process controllerfails, the primary process controller holds the primary status. A faultyprocess controller should be replaced online by a new one thatimmediately obtains the secondary status. The diagnostic provides allfunctions described above.

The diagnostic shown in FIG. 10 contains two identical circuits 210 eachof which includes a serial peripheral interface (SPI) 215 with masterand slave parts and Quad SPDT CMOS electronic switches 254. Circuits 215a, 254 a and 215 b, 254 b are embedded into PC A and PC B respectively.Circuit 215 a uses outputs IN 1, IN 2 to set switches S1 a, S2 a in 1position, and uses outputs IN 3, IN4 to switch S3 a, S4 a in 1 positionfor testing SPI 215 a before communicating with SPI 215 b. Similarly,circuit 215 b uses outputs IN 3, IN 4 to set switches S3 b, S4 b in 1position, and uses outputs IN 2, IN 1 to switches S2 b, S1 b in 1position for testing SPI 215 b before communicating with SPI 215 a. PC A74 a then uses master of SPI 215 a for sending predetermined bytes ofData OUT accompanied with CLK OUT pulses to DATA IN of the slave part ofthe SPI 215 a. PC A then compares Data OUT with DATA IN, and if nodiscrepancies are discovered, then SCI 215 a operates correctly,otherwise PC A repeats the sending/receiving of data between the masterand slave and indicates the failure of PC A or SPI 215 a, if thisfailure is a hard (permanent) failure. Similarly, PC B compares Data OUTwith DATA IN that is in the slave part obtained from master part of theSPI 215 b. If no discrepancies between Data Out and Date In arediscovered then SPI 215 b operates correctly, otherwise SC B repeats thesending/receiving of data between the master and slave, and indicates afailure of SC B or SPI 215 b, if this failure a hard (permanent)failure.

Continuing, the testing of switches Sa1-Sa4 is considered. PC A sets atmoment t1 (FIG. 10 low side) a signal IN 1 in high state. The switch S1a must pass from an OFF state (position 1) to an ON state (position 2)if it is not fails. If there are no faults discovered, PC A then sets IN1 at moment t2 in a low state for checking the ability of switch S1 a topass from an ON state back to an OFF state.

If Data IN still exists, it does mean that either switch S1 a fails, orthat IN 1 signal fails. The ability of switches S2 a, S3 a, and S4 a topass from an OFF state to an ON state and back are checked similarly asis performed with S1 a. SPI 215 a operates correctly if it switches S1a-S4 a from OFF to ON and back properly, as shown in FIG. 10. Thisself-test of SPI 215 a is completed at moment t9. All switches are in ONstate (position 2) at moment t9, allowing the SPI 215 a to be ready forcommunicating with neighboring SPI 215 b. SPI 215 b operates in the sameway as SPI 215 a due to the symmetrical SPI configuration. SPI 215 a andSPI 215 b operations, however, can be shifted in time.

The PC A and PC B initially set signals Ready IN as inputs. In addition,the PC A and PC B set initial signal IN 5 in a low state for settingswitches S5 a and S5 b in an OFF state (position 1). PC A then togglesthe Ready OUT signal from a high to a low state and back a few times tocheck whether the Ready Check signal will follow the Ready OUT signal ornot. When the testing of the SPI 215 a-b is successfully completed,switches S1 a-S5 a in PC A and switches S1 b-S5 b in SC B are in an ONstate. The PC A and the SC B then sends a Ready Out signal to each otherthrough buses 211-5 and 211-6. PC A and PC B begin synchronization inthe event that both receive a Ready Out signal on time. The PC A and PCB include a watchdog timer, which the PC A and the SC B sets forpredetermined time. In the event that one PC A does not obtain a “Ready”signal on time, it will to operate in a stand-alone mode. If PC A and PCB receive a “Ready OUT” signal on time, PC A and SC B are synchronized,and they send their status to each other. PC A and PC B compare theirstatuses and indicate a system failure if that statuses are the same asshown in FIG. 11 at block 302. Primary or secondary statuses for PC Aand for PC B are automatically defined at start-up by their location inthe main chassis 108. Master SPI sends the status of PC A to slave SPIof PC B over bus 211-2 (Data Out) and 211-1 (Clock OUT), while masterSPI sends status to the PC B to slave SPI of the PC A over bus 211-3(Data Out) and 211-4 (Clock Out). SPI 215 a and SPI 215 b operate,therefore, in full duplex mode. In addition, the PC A and the PC Bemploy conventional SEC-DED technology for correcting any single faultsduring communication and indicating the occurrence of multiple faults.

The details of the operation of the control section 14 b are shown inFIGS. 11AA-AC for the primary processor PC A (that is located on theleft side of the backplane) and in FIG. 11BA-BC for the secondaryprocessor PC B (that is located on the right side of the backplane). ThePC A and the PC B both obtain a new start status (NS) and implementsteps 302-310 after power up. The PC A and the PC B read their ownidentification word (ID) at step 310, and they obtain a real status ofFFh and 00 h at steps 312 and 322 respectively.

The PC A and the PC B checks the SPI 215 again at steps 316, 326 and, if“Ready IN” signal is received on time, they receive input data from theassociated IOC. In the event that PC A does not receive the “Ready IN”signal on time from PC B, PC A operates in a stand-alone modeimplementing the sequences of steps 332-336 until the faulty processcontroller is replaced. Further, in some embodiments, the controlsection 14 b uses a function block diagram (FBD) language for theapplication program development. The PC A sends a copy of a current FBaddress to the SC B over SPI 215 at step 318. At step 318 PC A alsosends PC B current variables. The PC A and PC B execute the firstfunction block (FB) of the application program respectively at steps320, 330. The PC A and PC B then update FB address to use this addressin the next scan of operation. If PC A does not obtain a Ready IN signalon time, the PC A indicates that the PC B or SPI 215 b has failed. Inthis event, primary PC A will operate in a stand-alone mode, as shown inFIG. 11AA, steps 332-336. If secondary PC B does not obtain a Ready INsignal on time, the PC B indicates that the PC A or SPI 215 a hasfailed. In the event, that healthy PC B obtains the primary status andwill operate in a stand-alone mode, as shown in FIG. 11BA, steps332-336.

Only PC A sends the outputs of the application program to the associatedIOC at step 320, and takes an address of FB that will execute in thenext scan. The address of the recent FB and variables are updated at theend of each scan, except the first one. The PC B operates similarly asPC A, but PC B does not send outputs of the FB execution to the IOC. ThePC B, however, updates the FB address and the current variables at step330 (FIG. 11BA-BC), because of the PC B will use them in the event thatPC A fails. During fault free operation, the PC A and PC B proceed againto step 302 to execute in each scan all the functions that have beenpreviously described. If the PC A or PC B fails, a healthy one replacesthe faulty one. The method described here for the control section ismore effective than many others are.

In conclusion, the safety section 14 a, thereby, further increases thesafety level of the control section 14 b that depicted in FIG. 9. Thecontrol section and the safety section operate independently, and havephysical separation protection layers, and as a result the integratedsystem ISC matches the up to SIL 3 requirements in accordance toStandards IEC 61511-1 11.2.4.

The advantages of the ISC system include: increased reliability andavailability of both safety and control functions matching up to SIL 3requirements of IEC 61508/61511 Standards; the ability to operate withfewer processes at the same time by using multiple I/O remote chassisthat are located away from the main chassis closer to controlledprocesses; and a reduction in the probability of common cause failuresby using different hardware and software in the control and safetyparts.

It should be appreciated that the various embodiments of the systemdiscussed above may include an electronic backplane or interconnectboard, which includes multiple interface ports or connectors forelectrically connecting the various system modules and components sothat they may communicate with each other in the manner necessary tocarry out the various functions discussed herein. For example, in someembodiments, the primary processor modules (PPMs A-C) may be on one sideof the backplane, while another side of the backplane includes thesupplemental processor modules (SPMs A-C). In some embodiments, the PPMsmay be positionally offset from that of the SPMs. The backplane alsoincludes various other removable or fixed interfaces or connectors toallow the other components of the various system embodiments to beattached thereto. In addition, the power supplies and communicationinterface modules utilized by the systems of the various embodiments mayalso be electrically coupled to the backplane.

In addition, it should be appreciated, that the output module includesan output controller, a 2-of-3 voter component, an ISD component, alogic circuit, and an output-voting network. Such features arebeneficial in that it allows the user to remove and replace the outputmodule if it fails. In some embodiments, the output controller, 2-of-3voter component, ISD component, and logic circuit may be implemented asfield-programmable gate array (FPGA), or as a complex programmable logicdevice (CPLD) for example.

It should be appreciated that various modifications and substitutions ofthe components of the various embodiments presented may be readily made.For example, the circuit in remote chassis shown in FIG. 9 can bemodified by using circuit FIG. 7 that houses the appropriate IOC A-Binstead of CP A and CP B. This modification can be utilized for moreresponsible applications, since it provides a higher level of faulttolerance and reliability than the circuit in the remote chassis shownin FIG. 9. Minor changes can be made in for logic circuit 53 and 69 thatallow the safety section to perform 1-of-2D instead of 2-of-2D shutdownlogic. The system can also support a hot spare input and output module,which take control if a fault is detected in the primary I/O moduleduring operation. These and others modifications may be made withoutdeparting from the spirit of the various embodiments disclosed.

Therefore, it can be seen that the objects of the various embodimentsdisclosed herein have been satisfied by the structure and its method foruse presented above. While in accordance with the Patent Statutes, onlythe best mode and preferred embodiments have been presented anddescribed in detail, with it being understood that the embodimentsdisclosed herein are not limited thereto or thereby. Accordingly, for anappreciation of the true scope and breadth of the embodiments, referenceshould be made to the following claims.

What is claimed is:
 1. A redundant computer system comprising: a firstchannel, a second channel, and a third channel each channel comprising:a primary processor; a secondary processor, wherein said primaryprocessor is in operative communication with said secondary processor,said primary and secondary processor operate in parallel redundancy;said primary processor in the first channel, said primary processor inthe second channel, and said primary processor in the third channel arein operative communication with each other; said secondary processor inthe first channel, said secondary processor in the second channel, andsaid secondary processor in the third channel are in operativecommunication with each other; an input module includes in each channela first and a second interface to provide operative communication ofsaid input module with said primary and secondary processor, whereinsaid input module in each channel is in operative communication with afirst and a second section of a dual redundant sensor (DRS) for eachcontrolled point that delivers input data to said input module; saidinput module including means for calculating a deviation between valuesof said input data produced by said first and second section of the DRSfor each controlled point to indicate whether said deviation is within apredetermined limit; said input module can be digital or analog; saidprimary processor and said secondary processor in each channelconfigured to receive said input data from said input module tosynchronously execute an application program and to transfer output dataas a result of said application program execution to an output modulevia a first and a second interface; said output module in each channelincludes an output controller that is in operative communication withsaid PPM and with said SPM for receiving said output data from the PPMand from the SPM; said output module further includes a voter componentand an improper sequence detector (ISD) component; said output modulecan be digital or analog; said voter component is in operativecommunication with said PPM and said SPM, said ISD component is inoperative communication with said voter component and with said outputcontroller; means in said improper sequence detector that verifies anabsence or presence a fault in timetable and verifies consistency ofprogram operations in said output controller; a comparing diagnostic insaid primary processor module (PPM) and said secondary processor module(SPM) in each channel for monitoring a condition of said output module,said comparing diagnostic includes a voter component and includes animproper sequence detector (ISD) component; said comparison diagnosticallows the system to disable said output module if at least two elementsamong the PPM, the SPM, and the ISD vote that said output controller hasfailed; said comparison diagnostic having no single point of failure toallow the system to operate with one operational output module in theevent that two neighboring output modules fail concurrently; said outputcontroller connected via a read only bus with a neighboring outputcontroller to receive or send said output data from or to saidneighboring output controllers; means wherein said output controllerincludes for activating a disparity signal on an input of said logiccircuit for some controlled points if the associated PPM and SPM producesaid output data that are different due to occurrence of transientfaults, or due to said deviation that is out of said predeterminedlimits for said controlled points; said disparity signal being activatedas a result of an exclusive NOR (XNOR) operation between single-bitoutput data that said output controller receives from the associated PPMand SPM; said output data is substituted by the output data produced byneighboring output controllers for some controlled points if saiddisparity signal is activated for said controlled points; said logiccircuit includes in each channel an arrangement of a plurality of logicgates that are coupled through isolated drivers with inputs of saidvoting network for each controlled point; said logic circuit in saidfirst channel providing the outputs of the associated voting network asa product of said output data that is received from said outputcontroller in the first channel and a sum of said output data receivedfrom output controllers in said second and third channels; said logiccircuit in said second channel providing outputs of the associatedvoting network as a product of said output data that is received fromsaid output controller in said second channel and a sum of said outputdata received from said output controllers in said first and thirdchannels; said logic circuit in said third channel providing outputs ofthe associated voting network as a product of said output data that isreceived from said output controller in said third channel and a sum ofsaid output data received from said output controllers in said first andsecond channels; said logic circuit and voting network performing alogic operation with said output data to provide 2-of-3 voting amongoutput data produced by said first, second, and third channel; saidvoting network including a fault recovery valve for each controlledpoint to allow said voting network to remain operational in the presenceof up two faults; the system continuing to perform 2-of-3 voting eventhough three PPMs or three SPMs concurrently fail, thereby, allowing thesystem to continue to remain operational in the presence of multiplefaults in the PPM and in the SPM; the system energizes a controlledprocess in the fault free operation when a majority of system channelsoperate properly and de-energizes said process in the presence ofmultiple dangerous failures in the system; the system continues tooperate in the presence of any two faults in one or two channels, thesystem providing a safe shutdown for the process if hard faults occursin all channels; each PPM uses same hardware and same software, whichare different with hardware and software that each SPM uses, saidhardware and software diversity allows the system decreasing theprobability of common cause failure.
 2. The redundant computer system ofclaim 1, wherein: said voter component includes a plurality of parallelvoting groups that are coupled between a voltage source and a groundnode, with each voting group including at least two low power switches,such as a MOSFET or any other suitable transistor or relay for example,connected in series; said primary and secondary processor in eachchannel continually controlling said switches in two groups by theassociated lines, while the switches in the third group is controlled bysaid ISD; said voter component produces an output signal as a result ofa majority of two-out-of-three voting among signals, which the primaryand a secondary processor and the ISD produce on the inputs of saidvoter component; said output signal in each channel is connected to acorresponding input of said logic circuit that disconnects output of theassociated channel from output of the system if said majority oftwo-out-of-three signals vote that said output controller fails; a logiccircuit in each channel includes an arrangement of plurality of a logicgates, the inputs of said arrangement is in operative communication withsaid output controller; outputs of said arrangement is in operativecommunication with inputs of said voting network via an isolationdrivers; said logic circuit is in operative communication with saidoutput controller and in operative communication with said votingnetwork, said voting network includes three switches in series for eachcontrolled point that is in operative communication with said logiccircuit, said three switches in said first, second, and third channelsare coupled in parallel for each controlled point for providing anoutput of the system; in normal operation, the system performs 2-of-3voting among output data produced by said first, second, and thirdchannel; a single output controller excludes an own output data fromoutputs of said logic circuit and uses output data received from theneighboring output controllers, the system then performs the 2-of-2voting instead of 2-of-3 voting if said disparity signal is activated insaid single output controller for some controlled points; said outputcontrollers in two channels excludes an own output data from outputs ofsaid associated logic circuits and uses output data received from theneighboring output controllers, the system then performs the 1-of-2voting instead of 2-of-3 voting if said disparity signal activates insaid two channels of the system for some controlled points; the system,continues to operate in the presence of said disparity in one or twochannels, the system may perform a safe shutdown for the process, ifsaid disparity occurs in all channels concurrently.
 3. A redundantcomputer system comprising: a first channel, and a second channel, eachchannel comprising: a primary processor; a secondary processor, whereinsaid primary processor is in operative communication with said secondaryprocessor; said primary and secondary processor operate in parallelredundancy; said primary processor in the first channel and said primaryprocessor in the second channel are in operative communication with eachother; said secondary processor in the first channel and said secondaryprocessor in the second channel are in operative communication with eachother; an input module includes in each channel a first and a secondinterface to provide operative communication of said input module withsaid primary and secondary processor, said input module can be digitalor analog module; said input module in each channel is in operativecommunication with a first and a second section of a dual redundantsensor (DRS) for each controlled point that deliver an input data tosaid input module; means in said input module for calculating adeviation between values of said input data produced by said first andin second section of the DRS for each controlled point to indicatewhether said deviation is within predetermined limits or not; saidprimary processor and said secondary processor in each channel receivesaid input data for synchronously execute an application program and fortransfer an output data as a result of said application programexecution to an output module via a first and a second interface; saidoutput module can be digital or analog; said output module in eachchannel includes an output controller, said voter and improper sequencecomponents, a logic circuit and a voting network; said output module canbe digital or analog; said voter component is in operative communicationwith said PPM and said SPM, said ISD component is in operativecommunication with said voter component and with said output controller;said comparison diagnostic in said primary processor (PPM) and saidsecondary processor (SPM) in each channel for monitoring condition ofsaid output module, said diagnostic includes a voter component andincludes an improper sequence detector (ISD) component; said comparisondiagnostic allows the system for disabling said output module if atleast two elements among the PPM, the SPM, and the ISD vote that theoutput controller fails; means in said improper sequence detector thatverify absence or presence a fault in timetable and verify consistencyof program operations in an output module, said output module inoperative communication with said primary processor and said secondaryprocessor and with said ISD component; said output controller connectedvia a read only bus with a neighboring output controller forreceiving/sending said output data from/to said neighboring outputcontroller; means in said output controller for activating a disparitysignal on input of said logic circuit for some controlled points if theassociated primary and secondary processor produce said output data thatare different due to occurrence of transient faults, or due to saiddeviation that is out of said predetermined limits for said controlledpoints; said disparity signal is activated as a result of an ExclusiveNOR (XNOR) operation between single-bit output data that said outputcontroller receives from the associated PPM and SPM; the primaryprocessor and the secondary processor in each channel use said inputdata for synchronously execute an application program and for transferan output data as a result of said application program execution to saidoutput controller in said output module; said logic circuit and votingnetwork perform a logic operation with said output data to provide2-of-2 voting among output data produced by said first and secondchannel of the system, said voting network includes a fault recoveryvalve for each controlled point to provide no single point of failure ofsaid voting network; said voting networks includes plurality switches inseries, said switches in said first and second channels connected inparallel to provide output of the system; the system performs said2-of-2 voting even though only two PPM or two SPM are operational; thesystem, thereby, continues to be operational in the presence of any twofaults in said PPM and said SPM; said output controller connected via aread only buses with neighboring output controller for receiving/sendingsaid output data from/to said neighboring output controller; said outputcontroller excludes an own output data from inputs of said logic circuitand uses output data receiving from the neighboring output controller,the system then performs the 1-of-2 voting instead of 2-of-2 voting ifsaid disparity signal activates in said output controller for somecontrolled points; the system, thereby, continues operate in thepresence of said disparity in one channel, the system may perform a safeshutdown for the process, if said disparity occurs in first and secondchannel concurrently; said logic circuit is in operative communicationwith said output controller and in operative communication with saidvoting network, which contains multiple switches in series for eachcontrolled points, said switches in said first and second channelsconnected in parallel; said logic circuit in said first channel providesoutputs of the associated voting network as a product of said outputdata received from said output controller in said first channel and asum of said output data receiving from output controllers in said firstand second channel; said logic circuit in said second channel providesoutputs of the associated voting network as a product of said outputdata received from said output controller in said second channel and asum of said output data receiving from output controllers in said secondand first channel.
 4. A redundant computer system comprising: a firstchannel, a second channel each channel comprising: a first centralprocessor and a second central processor that operate in parallelredundancy; said first central processor is in operative communicationwith said secondary central processor; a first input module and a secondinput module is in operative communication with said first centralprocessor and with said second central processor via the associatedinterfaces; said first input module and said second input module iscoupled with a single sensor for each controlled point for delivering aninput data of the process to the first processor and to the secondprocessor respectively; said first and second control processor use saidinput data for synchronously execute an application program and fortransfer an output data as a result of said application programexecution to said output module in normal system operation; said outputmodule includes an output controller, a voter and an improper sequencecomponents, a logic circuit, and a voting network; said first outputcontroller is in operative communication with said first centralprocessor via said first interface and is in operative communicationwith said second central processor via said second interface; saidsecond output controller is in operative communication with said secondcentral processor via said first interface and is in operativecommunication with said first central processor via said secondinterface; a first voter component and a second voter component that isin operative communication with said primary central processor and withsecondary central processor; an improper sequence detector that verifyabsence or presence a fault in timetable and verify a consistency ofprogram operations of said output controller; said output controller isin operative communication with the associated logic circuit in saidfirst and second channel; a comparing diagnostic in said first centralprocessor (FCP) and said second central processor (SCP) in each channelfor monitoring condition of said output module, said comparingdiagnostic includes a voter component and includes an improper sequencedetector (ISD) component; said comparison diagnostic allows the systemfor disabling said output module if at least two elements among the FCP,the SCP, and the ISD vote that said output controller fails; saidcomparison diagnostic having no single point of failure allows thesystem to operate with one working output controller in the event thatneighboring output controller fails; said output controller connectedvia a read only bus with a neighboring output controller forreceiving/sending said output data from/to said neighboring outputcontroller; said output controller activates a disparity signal oninputs of said logic circuit for some controlled points if said outputcontroller receive different data from said first and second controlprocessor due to occurrence of some transient faults; said disparitysignal is activated as a result of an Exclusive NOR (XNOR) operationbetween output data that said output controller receives from said firstand second central processors; said output data is substitutes by theoutput data produced by neighboring output controller for somecontrolled points if said disparity signal is activated for saidcontrolled points; the system continues operate if said disparity occursin only one output controller, the system performs a safe shutdown forthe process, if said disparity occurs in output controllers in saidfirst a second channels concurrently; said logic circuit is in operativecommunication with said output controller and in operative communicationwith a voting network, which contains multiple switches in series; saidswitches in said first a second channels connected in parallel for eachcontrolled point; each logic circuit and each voting network receivessaid output data from said first and second central processor via saidoutput controller, said logic circuit and voting network perform acertain logic operation with said output data to provide said 2-of-2voting among output data that produced by said first and second centralprocessor; means in said first and second central processor to use anadditional separate buses that provide operative communication with bothfirst and second output controllers; said means provide the systemcontinues to be operational in the presence of two faults: in firstcontrol processor and in second output controller, or in second centralprocessor and in first output controller; the system continues to beoperational in the presence of any single fault and may operate in thepresence of some kind of two faults; the system energizes controlledprocess in the fault free operation when both first and second centralprocessor and associating components operating properly and de-energizessaid process in the presence of two dangerous failures in the system. 5.A computer system integrating safety and control functionalitycomprising: a computer system integrating safety section and a controlsection that provide the system safety and control functionalityrespectively; a safety section includes at least one main chassishousing a first and a second channel, each channel comprising: a firstcentral processor and a second central processor that operate inparallel redundancy; said first and second central processor are locatedin a main chassis, means in said first and second central processors forcommunicating with said control section and with an external devicesover separated buses in redundant configuration; said first and secondcentral processors are in operative communication through a redundantbus for synchronizing their operation; said first and second centralprocessor has at least one ETHERNET port and at least one ETHERNETswitch for operative communicating with one or multiple remote chassisvia a first and a second input/output controller located on said remotechassis; said remote chassis may be located far away from the mainchassis to be nearer to controlled process; said communicating arecooper or fiber cables or can be wireless; each said remote chassisincludes: a first and a second input/output controller that is inoperative communication with said first central processor and with saidsecond central processor, a first and a second input module that is inoperative communication with said first and second input/outputcontroller, said first input module and said second input module iscoupled with said single sensor per controlled point for delivering aninput data of the process to said first and second central processorrespectively via the associated input/output controllers (IOC); saidfirst and second central processor uses said input data forsynchronously execute an application program and transfer said outputdata as a result of said application program execution to said first andsecond IOC under normal system operation; said IOC, in turn, transferssaid output data to said output module that includes an outputcontroller, said voter and improper sequence components, a logiccircuit, and a voting network; an improper sequence detector that verifyabsence or presence a fault in timetable and verify a consistency ofprogram operations of said output controller; the output controller isin operative communication with the associated voter component and withthe associated logic circuits in said first and second channel; adiagnostic in said first central processor (FCP) and said second centralprocessor (SCP) in each channel for monitoring condition of said outputmodule, said diagnostic includes in each channel a voter component andincludes an improper sequence detector (ISD) component; said diagnosticallows the system for disabling said output module if at least twoelements among the FCP, the SCP, and the ISD vote that said outputcontroller fails; said diagnostic having no single point of failureallows the system to operate with one working output controller in theevent that neighboring output controller fails; a logic circuit is inoperative communication with said output controller and in operativecommunication with said voting network, which contains multiple switchesin series; said switches in different voting networks connected inparallel for providing an output of the system for each controlledpoint; said logic circuit and said voting network perform a certainlogic operation with said output data to provide 2-of-2 voting amongoutput data that said first and second IOC receive from said first andsecond central processor; means in the first and second centralprocessor for energizing the process in the fault free operation whentwo input/output controllers and all associating modules and componentsoperating properly and de-energizing said process in the presence of twodangerous failures in the system; said control section housing at leasttwo process controllers arranged in back-up redundant configuration,said process controllers perform control functions without interruptsfrom said safety section until a critical parameters of controlledprocess are in the safe range; said control section includes at leastone main chassis housing a primary and a secondary process controller,that are in operative communication each to other through a first and asecond interface and a redundant bus; means in said first and secondaryprocess controller for communicating with said safety section and withan external devices over separated buses; said primary and secondarycentral processor has at least one ETHERNET port and at least oneETHERNET switch for operative communicating with one or multiple remotechassis via the associated input/output controller located on saidremote chassis; said remote chassis may be located far away from themain chassis to be nearer to controlled process; said communicating arecooper or fiber cables, or can be wireless; each said remote chassisincludes a multiple input and output modules that are in operativecommunicate with said first and second input/output controllers; saidprimary and secondary central processor obtains an input data from saidinput modules via said input/output controllers and uses said input datafor synchronously execute an application program; means in said processcontroller to select one process controller as a primary processcontroller, while identify the neighboring process controller as asecondary process controller; said first and second interface include aself-diagnostic and a mutual diagnostic for discovering possible faultsoccurrence in said primary and in said secondary process controllerrespectively and for disabling said first or second process controllerwhen it fails; method in hardware and software in each processcontroller to use said first and second interface for providing: saidprocess controller to obtain a primary status or a secondary statusdepends on location in said backplane; select only said primary processcontroller for sending output data as result of said control programexecution to the system control outputs, for allowing said primaryprocess controller to hold said primary status and operating in astand-alone mode in the event that said neighboring process controllerfails; said secondary process controller changes a secondary status tosaid primary status and performs control function in said stand-alonemode in the event that said primary process controller fails; saidfaulty process controller can be online removing and replacing by a newprocess controller, status of said new process controller isautomatically setting up as a new status after inserting said newprocess controller into a backplane, and then automatically changed fromnew status to secondary status during a current cycle of said controlsection operation; said new process controller is then reprogramming bythe neighboring processor that holds said primary status; means in saidprimary and in secondary controller to switch said serial interface fromsaid self-diagnostic to a mutual diagnostic by using a number of anelectronic Single-Pole Double-Throw (SPDT) switches; means in saidsecondary process controller to change status from secondary status toprimary status and starts operating in said stand-alone mode if saidprimary process controller fails; means in said primary processcontroller to keep primary status after going to said stand-alone modein the event that secondary process controller fails; said first andsecond interface in said primary and in secondary process controller isfor transmitting/receiving said self-diagnostic data and said status tosaid primary and secondary process controller respectively.
 6. Aredundant control system of claim 5 wherein: said primary and secondaryprocess controllers are identical; means in said process controllers fordefining said primary status or said secondary status after insertingsaid process controllers in said backplane and power up; said backplaneincludes a first socket connector located on the left side of saidbackplane and includes a second socket connector located on the rightside of said backplane; selected pins of said first socket connectorconnected to plus terminal of a power supply to form a firstidentification word, while selected pins of said second socket connectorconnected to ground terminal of said power supply to form a secondidentification word; a first and a second input port in each of saidprocess controllers, said input port coupled with a plug connector forinserting each process controller either to left side or to right sideof said backplane; if one said process controller inserted to left sideof said backplane it is coupled with a first socket connector, said oneprocess controller reads a first identification word via said firstinput port and gets said primary status after power up; if anotherprocess controller inserted to right side of said backplane it iscoupled with a second socket connector said another process controllerreads a second identification word via said second input port and getssaid secondary status after power up; said primary status and saidsecondary status of said process controllers are setting therebyinitially after system power up, but can be changed during systemoperation; said first and second interface is a serial peripheralinterface (SPI) in said primary and in secondary process controller fortransmitting/receiving said self-diagnostic data and status data to saidprimary and secondary process controller respectively; means in saidprimary and in secondary process controller to switch said SPI from saidself-diagnostic to an exchange said status data by using a number of anelectronic Single-Pole Double-Throw (SPDT) switches; further means insaid primary and in secondary process controller for continuouslyindicate primary or secondary status of said controllers; said primaryand secondary process controller can be remove and replace by newhealthy process controller if primary or secondary process controllerfails; status of said new healthy process controller is automaticallysetting up as new start status after power up, and then automaticallychanged to secondary status not later than during of one cycle of saidcontrol section operation; said SPI interfaces for discovering possiblefaults occurrence in the primary or in the secondary process controllerrespectively and disabling the primary or secondary process controllerwhen it fails; said SPI interfaces can operate in full Duplex mode.